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11a0 20 20 69 6e 20 61 20 67 72 61 70 68 2e 0a 0a 20 20 20 20 52 65 74 75 72 6e 73 0a 20 20 20 20 2d ..in.a.graph.......Returns.....-
11c0 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 76 61 6c 69 64 20 3a 20 62 6f 6f 6c 0a 20 20 20 20 20 20 20 20 ------.....valid.:.bool.........
11e0 54 72 75 65 20 69 66 20 64 65 67 5f 73 65 71 75 65 6e 63 65 20 69 73 20 67 72 61 70 68 69 63 61 True.if.deg_sequence.is.graphica
1200 6c 20 61 6e 64 20 46 61 6c 73 65 20 69 66 20 6e 6f 74 2e 0a 0a 20 20 20 20 45 78 61 6d 70 6c 65 l.and.False.if.not.......Example
1220 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 3e 3e 3e 20 47 20 3d 20 6e 78 2e 47 72 s.....--------.....>>>.G.=.nx.Gr
1240 61 70 68 28 5b 28 31 2c 20 32 29 2c 20 28 31 2c 20 33 29 2c 20 28 32 2c 20 33 29 2c 20 28 33 2c aph([(1,.2),.(1,.3),.(2,.3),.(3,
1260 20 34 29 2c 20 28 34 2c 20 32 29 2c 20 28 35 2c 20 31 29 2c 20 28 35 2c 20 34 29 5d 29 0a 20 20 .4),.(4,.2),.(5,.1),.(5,.4)])...
1280 20 20 3e 3e 3e 20 73 65 71 75 65 6e 63 65 20 3d 20 28 64 20 66 6f 72 20 5f 2c 20 64 20 69 6e 20 ..>>>.sequence.=.(d.for._,.d.in.
12a0 47 2e 64 65 67 72 65 65 28 29 29 0a 20 20 20 20 3e 3e 3e 20 6e 78 2e 69 73 5f 76 61 6c 69 64 5f G.degree()).....>>>.nx.is_valid_
12c0 64 65 67 72 65 65 5f 73 65 71 75 65 6e 63 65 5f 68 61 76 65 6c 5f 68 61 6b 69 6d 69 28 73 65 71 degree_sequence_havel_hakimi(seq
12e0 75 65 6e 63 65 29 0a 20 20 20 20 54 72 75 65 0a 0a 20 20 20 20 54 6f 20 74 65 73 74 20 61 20 6e uence).....True......To.test.a.n
1300 6f 6e 2d 76 61 6c 69 64 20 73 65 71 75 65 6e 63 65 3a 0a 20 20 20 20 3e 3e 3e 20 73 65 71 75 65 on-valid.sequence:.....>>>.seque
1320 6e 63 65 5f 6c 69 73 74 20 3d 20 5b 64 20 66 6f 72 20 5f 2c 20 64 20 69 6e 20 47 2e 64 65 67 72 nce_list.=.[d.for._,.d.in.G.degr
1340 65 65 28 29 5d 0a 20 20 20 20 3e 3e 3e 20 73 65 71 75 65 6e 63 65 5f 6c 69 73 74 5b 2d 31 5d 20 ee()].....>>>.sequence_list[-1].
1360 2b 3d 20 31 0a 20 20 20 20 3e 3e 3e 20 6e 78 2e 69 73 5f 76 61 6c 69 64 5f 64 65 67 72 65 65 5f +=.1.....>>>.nx.is_valid_degree_
1380 73 65 71 75 65 6e 63 65 5f 68 61 76 65 6c 5f 68 61 6b 69 6d 69 28 73 65 71 75 65 6e 63 65 5f 6c sequence_havel_hakimi(sequence_l
13a0 69 73 74 29 0a 20 20 20 20 46 61 6c 73 65 0a 0a 20 20 20 20 4e 6f 74 65 73 0a 20 20 20 20 2d 2d ist).....False......Notes.....--
13c0 2d 2d 2d 0a 20 20 20 20 54 68 65 20 5a 5a 20 63 6f 6e 64 69 74 69 6f 6e 20 73 61 79 73 20 74 68 ---.....The.ZZ.condition.says.th
13e0 61 74 20 66 6f 72 20 74 68 65 20 73 65 71 75 65 6e 63 65 20 64 20 69 66 0a 0a 20 20 20 20 2e 2e at.for.the.sequence.d.if........
1400 20 6d 61 74 68 3a 3a 0a 20 20 20 20 20 20 20 20 7c 64 7c 20 3e 3d 20 5c 66 72 61 63 7b 28 5c 6d .math::.........|d|.>=.\frac{(\m
1420 61 78 28 64 29 20 2b 20 5c 6d 69 6e 28 64 29 20 2b 20 31 29 5e 32 7d 7b 34 2a 5c 6d 69 6e 28 64 ax(d).+.\min(d).+.1)^2}{4*\min(d
1440 29 7d 0a 0a 20 20 20 20 74 68 65 6e 20 64 20 69 73 20 67 72 61 70 68 69 63 61 6c 2e 20 20 54 68 )}......then.d.is.graphical...Th
1460 69 73 20 77 61 73 20 73 68 6f 77 6e 20 69 6e 20 54 68 65 6f 72 65 6d 20 36 20 69 6e 20 5b 31 5d is.was.shown.in.Theorem.6.in.[1]
1480 5f 2e 0a 0a 20 20 20 20 52 65 66 65 72 65 6e 63 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 2d _.......References.....---------
14a0 2d 0a 20 20 20 20 2e 2e 20 5b 31 5d 20 49 2e 45 2e 20 5a 76 65 72 6f 76 69 63 68 20 61 6e 64 20 -........[1].I.E..Zverovich.and.
14c0 56 2e 45 2e 20 5a 76 65 72 6f 76 69 63 68 2e 20 22 43 6f 6e 74 72 69 62 75 74 69 6f 6e 73 20 74 V.E..Zverovich.."Contributions.t
14e0 6f 20 74 68 65 20 74 68 65 6f 72 79 0a 20 20 20 20 20 20 20 6f 66 20 67 72 61 70 68 69 63 20 73 o.the.theory........of.graphic.s
1500 65 71 75 65 6e 63 65 73 22 2c 20 44 69 73 63 72 65 74 65 20 4d 61 74 68 65 6d 61 74 69 63 73 2c equences",.Discrete.Mathematics,
1520 20 31 30 35 2c 20 70 70 2e 20 32 39 32 2d 33 30 33 20 28 31 39 39 32 29 2e 0a 20 20 20 20 2e 2e .105,.pp..292-303.(1992)........
1540 20 5b 68 61 76 65 6c 31 39 35 35 5d 20 48 61 76 65 6c 2c 20 56 2e 20 22 41 20 52 65 6d 61 72 6b .[havel1955].Havel,.V.."A.Remark
1560 20 6f 6e 20 74 68 65 20 45 78 69 73 74 65 6e 63 65 20 6f 66 20 46 69 6e 69 74 65 20 47 72 61 70 .on.the.Existence.of.Finite.Grap
1580 68 73 22 0a 20 20 20 20 20 20 20 43 61 73 6f 70 69 73 20 50 65 73 74 2e 20 4d 61 74 2e 20 38 30 hs"........Casopis.Pest..Mat..80
15a0 2c 20 34 37 37 2d 34 38 30 2c 20 31 39 35 35 2e 0a 20 20 20 20 2e 2e 20 5b 68 61 6b 69 6d 69 31 ,.477-480,.1955.........[hakimi1
15c0 39 36 32 5d 20 48 61 6b 69 6d 69 2c 20 53 2e 20 22 4f 6e 20 74 68 65 20 52 65 61 6c 69 7a 61 62 962].Hakimi,.S.."On.the.Realizab
15e0 69 6c 69 74 79 20 6f 66 20 61 20 53 65 74 20 6f 66 20 49 6e 74 65 67 65 72 73 20 61 73 0a 20 20 ility.of.a.Set.of.Integers.as...
1600 20 20 20 20 20 44 65 67 72 65 65 73 20 6f 66 20 74 68 65 20 56 65 72 74 69 63 65 73 20 6f 66 20 .....Degrees.of.the.Vertices.of.
1620 61 20 47 72 61 70 68 2e 22 20 53 49 41 4d 20 4a 2e 20 41 70 70 6c 2e 20 4d 61 74 68 2e 20 31 30 a.Graph.".SIAM.J..Appl..Math..10
1640 2c 20 34 39 36 2d 35 30 36 2c 20 31 39 36 32 2e 0a 20 20 20 20 2e 2e 20 5b 43 4c 31 39 39 36 5d ,.496-506,.1962.........[CL1996]
1660 20 47 2e 20 43 68 61 72 74 72 61 6e 64 20 61 6e 64 20 4c 2e 20 4c 65 73 6e 69 61 6b 2c 20 22 47 .G..Chartrand.and.L..Lesniak,."G
1680 72 61 70 68 73 20 61 6e 64 20 44 69 67 72 61 70 68 73 22 2c 0a 20 20 20 20 20 20 20 43 68 61 70 raphs.and.Digraphs",........Chap
16a0 6d 61 6e 20 61 6e 64 20 48 61 6c 6c 2f 43 52 43 2c 20 31 39 39 36 2e 0a 20 20 20 20 46 72 02 00 man.and.Hall/CRC,.1996......Fr..
16c0 00 00 e9 04 00 00 00 72 17 00 00 00 54 a9 04 72 27 00 00 00 72 0e 00 00 00 72 1c 00 00 00 da 05 .......r....T..r'...r....r......
16e0 72 61 6e 67 65 29 0b 72 1f 00 00 00 72 22 00 00 00 72 23 00 00 00 72 24 00 00 00 72 25 00 00 00 range).r....r"...r#...r$...r%...
1700 72 21 00 00 00 da 08 6d 6f 64 73 74 75 62 73 da 05 6d 73 6c 65 6e da 01 6b da 01 69 da 04 73 74 r!.....modstubs..mslen..k..i..st
1720 75 62 73 0b 00 00 00 20 20 20 20 20 20 20 20 20 20 20 72 14 00 00 00 72 08 00 00 00 72 08 00 00 ubs...............r....r....r...
1740 00 60 00 00 00 73 92 01 00 00 80 00 f0 68 01 03 05 15 dc 28 3e b8 7c d3 28 4c d1 08 25 88 04 88 .`...s.......h.....(>.|.(L..%...
1760 64 90 44 98 21 98 58 f0 08 00 08 09 88 41 82 76 90 11 90 54 91 18 98 41 91 1c a0 24 a8 14 a1 2b d.D.!.X......A.v...T...A...$...+
1780 b0 01 a1 2f b0 64 b8 54 b1 6b c0 41 b1 6f d1 21 46 d2 11 46 d8 0f 13 e0 10 11 88 73 90 64 98 51 .../.d.T.k.A.o.!F..F.......s.d.Q
17a0 91 68 d1 0f 1f 80 48 e0 0a 0b 88 61 8a 25 e0 0e 16 90 74 89 6e a0 01 d2 0e 21 d8 0c 10 90 41 89 .h....H....a.%....t.n....!....A.
17c0 49 88 44 f0 03 00 0f 17 90 74 89 6e a0 01 d3 0e 21 f0 08 00 0c 10 90 21 90 61 91 25 8a 3c d8 13 I.D......t.n....!......!.a.%.<..
17e0 18 f0 06 00 1d 25 a0 54 99 4e a8 51 d1 1c 2e b0 01 b0 41 b1 05 d0 08 19 88 08 90 14 89 0e 98 01 .....%.T.N.Q......A.............
1800 e0 10 11 88 05 d8 0c 10 88 01 dc 11 16 90 74 93 1b f2 00 06 09 1b 88 41 d8 12 1a 98 31 91 2b a0 ..............t........A....1.+.
1820 11 d2 12 22 d8 10 11 90 51 91 06 90 01 f0 03 00 13 1b 98 31 91 2b a0 11 d3 12 22 e0 1d 25 a0 61 ..."....Q..........1.+...."..%.a
1840 99 5b a8 31 99 5f a8 61 b0 21 a9 65 88 4e 88 48 90 51 89 4b 98 11 d8 0f 10 90 31 8b 75 d8 22 23 .[.1._.a.!.e.N.H.Q.K......1.u."#
1860 a0 61 a1 25 90 08 98 15 91 0f d8 10 15 98 11 91 0a 91 05 f0 0d 06 09 1b f4 10 00 12 17 90 75 93 .a.%..........................u.
1880 1c f2 00 02 09 3a 88 41 d8 13 1b 98 41 91 3b 88 44 d8 20 28 a8 14 a1 0e b0 11 d1 20 32 b0 41 b8 .....:.A....A.;.D..(........2.A.
18a0 01 b1 45 d0 0c 1d 88 48 90 54 89 4e 99 41 f0 05 02 09 3a f0 2d 00 0b 0c 88 61 8b 25 f0 32 00 0c ..E....H.T.N.A....:.-....a.%.2..
18c0 10 f8 f4 43 01 00 0c 0e d7 0b 20 d1 0b 20 f2 00 01 05 15 d9 0f 14 f0 03 01 05 15 fa 73 11 00 00 ...C........................s...
18e0 00 82 11 43 2c 00 c3 2c 13 44 02 03 c4 01 01 44 02 03 63 01 00 00 00 00 00 00 00 00 00 00 00 07 ...C,..,.D.....D..c.............
1900 00 00 00 03 00 00 00 f3 ba 01 00 00 97 00 09 00 74 01 00 00 00 00 00 00 00 00 7c 00 ab 01 00 00 ................t.........|.....
1920 00 00 00 00 5c 05 00 00 7d 01 7d 02 7d 03 7d 04 7d 05 7c 04 64 02 6b 28 00 00 73 1a 64 03 7c 02 ....\...}.}.}.}.}.|.d.k(..s.d.|.
1940 7a 05 00 00 7c 04 7a 05 00 00 7c 01 7c 02 7a 00 00 00 64 04 7a 00 00 00 7c 01 7c 02 7a 00 00 00 z...|.z...|.|.z...d.z...|.|.z...
1960 64 04 7a 00 00 00 7a 05 00 00 6b 5c 00 00 72 01 79 05 64 06 5c 04 00 00 7d 06 7d 07 7d 08 7d 09 d.z...z...k\..r.y.d.\...}.}.}.}.
1980 74 07 00 00 00 00 00 00 00 00 7c 01 7c 02 64 04 7a 0a 00 00 64 07 ab 03 00 00 00 00 00 00 44 00 t.........|.|.d.z...d.........D.
19a0 5d 76 00 00 7d 0a 7c 0a 7c 06 64 04 7a 00 00 00 6b 02 00 00 72 02 01 00 79 05 7c 05 7c 0a 19 00 ]v..}.|.|.d.z...k...r...y.|.|...
19c0 00 00 64 02 6b 44 00 00 73 01 8c 16 7c 05 7c 0a 19 00 00 00 7d 0b 7c 0a 7c 06 7c 0b 7a 00 00 00 ..d.kD..s...|.|.....}.|.|.|.z...
19e0 6b 02 00 00 72 05 7c 0a 7c 06 7a 0a 00 00 7d 0b 7c 07 7c 0b 7c 0a 7a 05 00 00 7a 0d 00 00 7d 07 k...r.|.|.z...}.|.|.|.z...z...}.
1a00 74 07 00 00 00 00 00 00 00 00 7c 0b ab 01 00 00 00 00 00 00 44 00 5d 1e 00 00 7d 0c 7c 08 7c 05 t.........|.........D.]...}.|.|.
1a20 7c 06 7c 0c 7a 00 00 00 19 00 00 00 7a 0d 00 00 7d 08 7c 09 7c 06 7c 0c 7a 00 00 00 7c 05 7c 06 |.|.z.......z...}.|.|.|.z...|.|.
1a40 7c 0c 7a 00 00 00 19 00 00 00 7a 05 00 00 7a 0d 00 00 7d 09 8c 20 04 00 7c 06 7c 0b 7a 0d 00 00 |.z.......z...z...}.....|.|.z...
1a60 7d 06 7c 07 7c 06 7c 04 64 04 7a 0a 00 00 7a 05 00 00 7c 06 7c 08 7a 05 00 00 7a 0a 00 00 7c 09 }.|.|.|.d.z...z...|.|.z...z...|.
1a80 7a 00 00 00 6b 44 00 00 73 01 8c 76 01 00 79 01 04 00 79 05 23 00 74 02 00 00 00 00 00 00 00 00 z...kD..s..v..y...y.#.t.........
1aa0 6a 04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 24 00 72 03 01 00 59 00 79 01 77 00 j...................$.r...Y.y.w.
1ac0 78 03 59 00 77 01 29 08 75 ef 07 00 00 52 65 74 75 72 6e 73 20 54 72 75 65 20 69 66 20 64 65 67 x.Y.w.).u....Returns.True.if.deg
1ae0 5f 73 65 71 75 65 6e 63 65 20 63 61 6e 20 62 65 20 72 65 61 6c 69 7a 65 64 20 62 79 20 61 20 73 _sequence.can.be.realized.by.a.s
1b00 69 6d 70 6c 65 20 67 72 61 70 68 2e 0a 0a 20 20 20 20 54 68 65 20 76 61 6c 69 64 61 74 69 6f 6e imple.graph.......The.validation
1b20 20 69 73 20 64 6f 6e 65 20 75 73 69 6e 67 20 74 68 65 20 45 72 64 c5 91 73 2d 47 61 6c 6c 61 69 .is.done.using.the.Erd..s-Gallai
1b40 20 74 68 65 6f 72 65 6d 20 5b 45 47 31 39 36 30 5d 5f 2e 0a 0a 20 20 20 20 50 61 72 61 6d 65 74 .theorem.[EG1960]_.......Paramet
1b60 65 72 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 64 65 67 5f 73 65 71 75 65 ers.....----------.....deg_seque
1b80 6e 63 65 20 3a 20 6c 69 73 74 0a 20 20 20 20 20 20 20 20 41 20 6c 69 73 74 20 6f 66 20 69 6e 74 nce.:.list.........A.list.of.int
1ba0 65 67 65 72 73 0a 0a 20 20 20 20 52 65 74 75 72 6e 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 0a 20 egers......Returns.....-------..
1bc0 20 20 20 76 61 6c 69 64 20 3a 20 62 6f 6f 6c 0a 20 20 20 20 20 20 20 20 54 72 75 65 20 69 66 20 ...valid.:.bool.........True.if.
1be0 64 65 67 5f 73 65 71 75 65 6e 63 65 20 69 73 20 67 72 61 70 68 69 63 61 6c 20 61 6e 64 20 46 61 deg_sequence.is.graphical.and.Fa
1c00 6c 73 65 20 69 66 20 6e 6f 74 2e 0a 0a 20 20 20 20 45 78 61 6d 70 6c 65 73 0a 20 20 20 20 2d 2d lse.if.not.......Examples.....--
1c20 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 3e 3e 3e 20 47 20 3d 20 6e 78 2e 47 72 61 70 68 28 5b 28 31 2c ------.....>>>.G.=.nx.Graph([(1,
1c40 20 32 29 2c 20 28 31 2c 20 33 29 2c 20 28 32 2c 20 33 29 2c 20 28 33 2c 20 34 29 2c 20 28 34 2c .2),.(1,.3),.(2,.3),.(3,.4),.(4,
1c60 20 32 29 2c 20 28 35 2c 20 31 29 2c 20 28 35 2c 20 34 29 5d 29 0a 20 20 20 20 3e 3e 3e 20 73 65 .2),.(5,.1),.(5,.4)]).....>>>.se
1c80 71 75 65 6e 63 65 20 3d 20 28 64 20 66 6f 72 20 5f 2c 20 64 20 69 6e 20 47 2e 64 65 67 72 65 65 quence.=.(d.for._,.d.in.G.degree
1ca0 28 29 29 0a 20 20 20 20 3e 3e 3e 20 6e 78 2e 69 73 5f 76 61 6c 69 64 5f 64 65 67 72 65 65 5f 73 ()).....>>>.nx.is_valid_degree_s
1cc0 65 71 75 65 6e 63 65 5f 65 72 64 6f 73 5f 67 61 6c 6c 61 69 28 73 65 71 75 65 6e 63 65 29 0a 20 equence_erdos_gallai(sequence)..
1ce0 20 20 20 54 72 75 65 0a 0a 20 20 20 20 54 6f 20 74 65 73 74 20 61 20 6e 6f 6e 2d 76 61 6c 69 64 ...True......To.test.a.non-valid
1d00 20 73 65 71 75 65 6e 63 65 3a 0a 20 20 20 20 3e 3e 3e 20 73 65 71 75 65 6e 63 65 5f 6c 69 73 74 .sequence:.....>>>.sequence_list
1d20 20 3d 20 5b 64 20 66 6f 72 20 5f 2c 20 64 20 69 6e 20 47 2e 64 65 67 72 65 65 28 29 5d 0a 20 20 .=.[d.for._,.d.in.G.degree()]...
1d40 20 20 3e 3e 3e 20 73 65 71 75 65 6e 63 65 5f 6c 69 73 74 5b 2d 31 5d 20 2b 3d 20 31 0a 20 20 20 ..>>>.sequence_list[-1].+=.1....
1d60 20 3e 3e 3e 20 6e 78 2e 69 73 5f 76 61 6c 69 64 5f 64 65 67 72 65 65 5f 73 65 71 75 65 6e 63 65 .>>>.nx.is_valid_degree_sequence
1d80 5f 65 72 64 6f 73 5f 67 61 6c 6c 61 69 28 73 65 71 75 65 6e 63 65 5f 6c 69 73 74 29 0a 20 20 20 _erdos_gallai(sequence_list)....
1da0 20 46 61 6c 73 65 0a 0a 20 20 20 20 4e 6f 74 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 0a 0a 20 20 20 .False......Notes.....-----.....
1dc0 20 54 68 69 73 20 69 6d 70 6c 65 6d 65 6e 74 61 74 69 6f 6e 20 75 73 65 73 20 61 6e 20 65 71 75 .This.implementation.uses.an.equ
1de0 69 76 61 6c 65 6e 74 20 66 6f 72 6d 20 6f 66 20 74 68 65 20 45 72 64 c5 91 73 2d 47 61 6c 6c 61 ivalent.form.of.the.Erd..s-Galla
1e00 69 20 63 72 69 74 65 72 69 6f 6e 2e 0a 20 20 20 20 57 6f 72 73 74 2d 63 61 73 65 20 72 75 6e 20 i.criterion......Worst-case.run.
1e20 74 69 6d 65 20 69 73 20 24 4f 28 6e 29 24 20 77 68 65 72 65 20 24 6e 24 20 69 73 20 74 68 65 20 time.is.$O(n)$.where.$n$.is.the.
1e40 6c 65 6e 67 74 68 20 6f 66 20 74 68 65 20 73 65 71 75 65 6e 63 65 2e 0a 0a 20 20 20 20 53 70 65 length.of.the.sequence.......Spe
1e60 63 69 66 69 63 61 6c 6c 79 2c 20 61 20 73 65 71 75 65 6e 63 65 20 64 20 69 73 20 67 72 61 70 68 cifically,.a.sequence.d.is.graph
1e80 69 63 61 6c 20 69 66 20 61 6e 64 20 6f 6e 6c 79 20 69 66 20 74 68 65 0a 20 20 20 20 73 75 6d 20 ical.if.and.only.if.the.....sum.
1ea0 6f 66 20 74 68 65 20 73 65 71 75 65 6e 63 65 20 69 73 20 65 76 65 6e 20 61 6e 64 20 66 6f 72 20 of.the.sequence.is.even.and.for.
1ec0 61 6c 6c 20 73 74 72 6f 6e 67 20 69 6e 64 69 63 65 73 20 6b 20 69 6e 20 74 68 65 20 73 65 71 75 all.strong.indices.k.in.the.sequ
1ee0 65 6e 63 65 2c 0a 0a 20 20 20 20 20 2e 2e 20 6d 61 74 68 3a 3a 0a 0a 20 20 20 20 20 20 20 5c 73 ence,..........math::.........\s
1f00 75 6d 5f 7b 69 3d 31 7d 5e 7b 6b 7d 20 64 5f 69 20 5c 6c 65 71 20 6b 28 6b 2d 31 29 20 2b 20 5c um_{i=1}^{k}.d_i.\leq.k(k-1).+.\
1f20 73 75 6d 5f 7b 6a 3d 6b 2b 31 7d 5e 7b 6e 7d 20 5c 6d 69 6e 28 64 5f 69 2c 6b 29 0a 20 20 20 20 sum_{j=k+1}^{n}.\min(d_i,k).....
1f40 20 20 20 20 20 20 20 20 20 3d 20 6b 28 6e 2d 31 29 20 2d 20 28 20 6b 20 5c 73 75 6d 5f 7b 6a 3d .........=.k(n-1).-.(.k.\sum_{j=
1f60 30 7d 5e 7b 6b 2d 31 7d 20 6e 5f 6a 20 2d 20 5c 73 75 6d 5f 7b 6a 3d 30 7d 5e 7b 6b 2d 31 7d 20 0}^{k-1}.n_j.-.\sum_{j=0}^{k-1}.
1f80 6a 20 6e 5f 6a 20 29 0a 0a 20 20 20 20 41 20 73 74 72 6f 6e 67 20 69 6e 64 65 78 20 6b 20 69 73 j.n_j.)......A.strong.index.k.is
1fa0 20 61 6e 79 20 69 6e 64 65 78 20 77 68 65 72 65 20 64 5f 6b 20 3e 3d 20 6b 20 61 6e 64 20 74 68 .any.index.where.d_k.>=.k.and.th
1fc0 65 20 76 61 6c 75 65 20 6e 5f 6a 20 69 73 20 74 68 65 0a 20 20 20 20 6e 75 6d 62 65 72 20 6f 66 e.value.n_j.is.the.....number.of
1fe0 20 6f 63 63 75 72 72 65 6e 63 65 73 20 6f 66 20 6a 20 69 6e 20 64 2e 20 20 54 68 65 20 6d 61 78 .occurrences.of.j.in.d...The.max
2000 69 6d 61 6c 20 73 74 72 6f 6e 67 20 69 6e 64 65 78 20 69 73 20 63 61 6c 6c 65 64 20 74 68 65 0a imal.strong.index.is.called.the.
2020 20 20 20 20 44 75 72 66 65 65 20 69 6e 64 65 78 2e 0a 0a 20 20 20 20 54 68 69 73 20 70 61 72 74 ....Durfee.index.......This.part
2040 69 63 75 6c 61 72 20 72 65 61 72 72 61 6e 67 65 6d 65 6e 74 20 63 6f 6d 65 73 20 66 72 6f 6d 20 icular.rearrangement.comes.from.
2060 74 68 65 20 70 72 6f 6f 66 20 6f 66 20 54 68 65 6f 72 65 6d 20 33 20 69 6e 20 5b 32 5d 5f 2e 0a the.proof.of.Theorem.3.in.[2]_..
2080 0a 20 20 20 20 54 68 65 20 5a 5a 20 63 6f 6e 64 69 74 69 6f 6e 20 73 61 79 73 20 74 68 61 74 20 .....The.ZZ.condition.says.that.
20a0 66 6f 72 20 74 68 65 20 73 65 71 75 65 6e 63 65 20 64 20 69 66 0a 0a 20 20 20 20 2e 2e 20 6d 61 for.the.sequence.d.if.........ma
20c0 74 68 3a 3a 0a 20 20 20 20 20 20 20 20 7c 64 7c 20 3e 3d 20 5c 66 72 61 63 7b 28 5c 6d 61 78 28 th::.........|d|.>=.\frac{(\max(
20e0 64 29 20 2b 20 5c 6d 69 6e 28 64 29 20 2b 20 31 29 5e 32 7d 7b 34 2a 5c 6d 69 6e 28 64 29 7d 0a d).+.\min(d).+.1)^2}{4*\min(d)}.
2100 0a 20 20 20 20 74 68 65 6e 20 64 20 69 73 20 67 72 61 70 68 69 63 61 6c 2e 20 20 54 68 69 73 20 .....then.d.is.graphical...This.
2120 77 61 73 20 73 68 6f 77 6e 20 69 6e 20 54 68 65 6f 72 65 6d 20 36 20 69 6e 20 5b 32 5d 5f 2e 0a was.shown.in.Theorem.6.in.[2]_..
2140 0a 20 20 20 20 52 65 66 65 72 65 6e 63 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 20 .....References.....----------..
2160 20 20 20 2e 2e 20 5b 31 5d 20 41 2e 20 54 72 69 70 61 74 68 69 20 61 6e 64 20 53 2e 20 56 69 6a ......[1].A..Tripathi.and.S..Vij
2180 61 79 2e 20 22 41 20 6e 6f 74 65 20 6f 6e 20 61 20 74 68 65 6f 72 65 6d 20 6f 66 20 45 72 64 c5 ay.."A.note.on.a.theorem.of.Erd.
21a0 91 73 20 26 20 47 61 6c 6c 61 69 22 2c 0a 20 20 20 20 20 20 20 44 69 73 63 72 65 74 65 20 4d 61 .s.&.Gallai",........Discrete.Ma
21c0 74 68 65 6d 61 74 69 63 73 2c 20 32 36 35 2c 20 70 70 2e 20 34 31 37 2d 34 32 30 20 28 32 30 30 thematics,.265,.pp..417-420.(200
21e0 33 29 2e 0a 20 20 20 20 2e 2e 20 5b 32 5d 20 49 2e 45 2e 20 5a 76 65 72 6f 76 69 63 68 20 61 6e 3).........[2].I.E..Zverovich.an
2200 64 20 56 2e 45 2e 20 5a 76 65 72 6f 76 69 63 68 2e 20 22 43 6f 6e 74 72 69 62 75 74 69 6f 6e 73 d.V.E..Zverovich.."Contributions
2220 20 74 6f 20 74 68 65 20 74 68 65 6f 72 79 0a 20 20 20 20 20 20 20 6f 66 20 67 72 61 70 68 69 63 .to.the.theory........of.graphic
2240 20 73 65 71 75 65 6e 63 65 73 22 2c 20 44 69 73 63 72 65 74 65 20 4d 61 74 68 65 6d 61 74 69 63 .sequences",.Discrete.Mathematic
2260 73 2c 20 31 30 35 2c 20 70 70 2e 20 32 39 32 2d 33 30 33 20 28 31 39 39 32 29 2e 0a 20 20 20 20 s,.105,.pp..292-303.(1992)......
2280 2e 2e 20 5b 45 47 31 39 36 30 5d 20 45 72 64 c5 91 73 20 61 6e 64 20 47 61 6c 6c 61 69 2c 20 4d ...[EG1960].Erd..s.and.Gallai,.M
22a0 61 74 2e 20 4c 61 70 6f 6b 20 31 31 20 32 36 34 2c 20 31 39 36 30 2e 0a 20 20 20 20 46 72 02 00 at..Lapok.11.264,.1960......Fr..
22c0 00 00 72 29 00 00 00 72 17 00 00 00 54 29 04 72 02 00 00 00 72 02 00 00 00 72 02 00 00 00 72 02 ..r)...r....T).r....r....r....r.
22e0 00 00 00 e9 ff ff ff ff 72 2a 00 00 00 29 0d 72 1f 00 00 00 72 22 00 00 00 72 23 00 00 00 72 24 ........r*...).r....r"...r#...r$
2300 00 00 00 72 25 00 00 00 72 21 00 00 00 72 2e 00 00 00 da 07 73 75 6d 5f 64 65 67 da 06 73 75 6d ...r%...r!...r......sum_deg..sum
2320 5f 6e 6a da 07 73 75 6d 5f 6a 6e 6a da 02 64 6b da 08 72 75 6e 5f 73 69 7a 65 da 01 76 73 0d 00 _nj..sum_jnj..dk..run_size..vs..
2340 00 00 20 20 20 20 20 20 20 20 20 20 20 20 20 72 14 00 00 00 72 07 00 00 00 72 07 00 00 00 ba 00 ...............r....r....r......
2360 00 00 73 4a 01 00 00 80 00 f0 40 02 03 05 15 dc 28 3e b8 7c d3 28 4c d1 08 25 88 04 88 64 90 44 ..sJ......@.....(>.|.(L..%...d.D
2380 98 21 98 58 f0 08 00 08 09 88 41 82 76 90 11 90 54 91 18 98 41 91 1c a0 24 a8 14 a1 2b b0 01 a1 .!.X......A.v...T...A...$...+...
23a0 2f b0 64 b8 54 b1 6b c0 41 b1 6f d1 21 46 d2 11 46 d8 0f 13 f0 06 00 23 2d d1 04 1f 80 41 80 77 /.d.T.k.A.o.!F..F......#-....A.w
23c0 90 06 98 07 dc 0e 13 90 44 98 24 a0 11 99 28 a0 42 d3 0e 27 f2 00 0d 05 1d 88 02 d8 0b 0d 90 01 ........D.$...(.B..'............
23e0 90 41 91 05 8a 3a d9 13 17 d8 0b 13 90 42 89 3c 98 21 d3 0b 1b d8 17 1f a0 02 91 7c 88 48 d8 0f .A...:.......B.<.!.........|.H..
2400 11 90 41 98 08 91 4c d2 0f 20 d8 1b 1d a0 01 99 36 90 08 d8 0c 13 90 78 a0 22 91 7d d1 0c 24 88 ..A...L.........6......x.".}..$.
2420 47 dc 15 1a 98 38 93 5f f2 00 02 0d 35 90 01 d8 10 16 98 28 a0 31 a0 71 a1 35 99 2f d1 10 29 90 G....8._....5......(.1.q.5./..).
2440 06 d8 10 17 98 41 a0 01 99 45 a0 58 a8 61 b0 21 a9 65 a1 5f d1 1b 34 d1 10 34 91 07 f0 05 02 0d .....A...E.X.a.!.e._..4..4......
2460 35 f0 06 00 0d 0e 90 18 89 4d 88 41 d8 0f 16 98 11 98 61 a0 21 99 65 99 1b a0 71 a8 36 a1 7a d1 5........M.A......a.!.e...q.6.z.
2480 19 31 b0 47 d1 19 3b d3 0f 3b d9 17 1c f0 1b 0d 05 1d f0 1c 00 0c 10 f8 f4 2d 00 0c 0e d7 0b 20 .1.G..;..;...............-......
24a0 d1 0b 20 f2 00 01 05 15 d9 0f 14 f0 03 01 05 15 fa 73 11 00 00 00 82 11 43 04 00 c3 04 13 43 1a .................s......C.....C.
24c0 03 c3 19 01 43 1a 03 63 01 00 00 00 00 00 00 00 00 00 00 00 06 00 00 00 03 00 00 00 f3 da 00 00 ....C..c........................
24e0 00 97 00 09 00 74 00 00 00 00 00 00 00 00 00 6a 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 .....t.........j................
2500 00 00 00 6a 05 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7c 00 ab 01 00 00 00 00 00 ...j...................|........
2520 00 7d 01 64 02 5c 02 00 00 7d 02 7d 03 7c 01 44 00 5d 1a 00 00 7d 04 7c 04 64 03 6b 02 00 00 72 .}.d.\...}.}.|.D.]...}.|.d.k...r
2540 02 01 00 79 01 7c 02 7c 04 7a 00 00 00 74 09 00 00 00 00 00 00 00 00 7c 03 7c 04 ab 02 00 00 00 ...y.|.|.z...t.........|.|......
2560 00 00 00 7d 03 7d 02 8c 1c 04 00 7c 02 64 04 7a 06 00 00 73 08 7c 02 64 04 7c 03 7a 05 00 00 6b ...}.}.....|.d.z...s.|.d.|.z...k
2580 02 00 00 72 01 79 01 79 05 23 00 74 00 00 00 00 00 00 00 00 00 6a 06 00 00 00 00 00 00 00 00 00 ...r.y.y.#.t.........j..........
25a0 00 00 00 00 00 00 00 00 00 24 00 72 03 01 00 59 00 79 01 77 00 78 03 59 00 77 01 29 06 61 ad 03 .........$.r...Y.y.w.x.Y.w.).a..
25c0 00 00 52 65 74 75 72 6e 73 20 54 72 75 65 20 69 66 20 73 6f 6d 65 20 6d 75 6c 74 69 67 72 61 70 ..Returns.True.if.some.multigrap
25e0 68 20 63 61 6e 20 72 65 61 6c 69 7a 65 20 74 68 65 20 73 65 71 75 65 6e 63 65 2e 0a 0a 20 20 20 h.can.realize.the.sequence......
2600 20 50 61 72 61 6d 65 74 65 72 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 73 .Parameters.....----------.....s
2620 65 71 75 65 6e 63 65 20 3a 20 6c 69 73 74 0a 20 20 20 20 20 20 20 20 41 20 6c 69 73 74 20 6f 66 equence.:.list.........A.list.of
2640 20 69 6e 74 65 67 65 72 73 0a 0a 20 20 20 20 52 65 74 75 72 6e 73 0a 20 20 20 20 2d 2d 2d 2d 2d .integers......Returns.....-----
2660 2d 2d 0a 20 20 20 20 76 61 6c 69 64 20 3a 20 62 6f 6f 6c 0a 20 20 20 20 20 20 20 20 54 72 75 65 --.....valid.:.bool.........True
2680 20 69 66 20 64 65 67 5f 73 65 71 75 65 6e 63 65 20 69 73 20 61 20 6d 75 6c 74 69 67 72 61 70 68 .if.deg_sequence.is.a.multigraph
26a0 69 63 20 64 65 67 72 65 65 20 73 65 71 75 65 6e 63 65 20 61 6e 64 20 46 61 6c 73 65 20 69 66 20 ic.degree.sequence.and.False.if.
26c0 6e 6f 74 2e 0a 0a 20 20 20 20 45 78 61 6d 70 6c 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 0a not.......Examples.....--------.
26e0 20 20 20 20 3e 3e 3e 20 47 20 3d 20 6e 78 2e 4d 75 6c 74 69 47 72 61 70 68 28 5b 28 31 2c 20 32 ....>>>.G.=.nx.MultiGraph([(1,.2
2700 29 2c 20 28 31 2c 20 33 29 2c 20 28 32 2c 20 33 29 2c 20 28 33 2c 20 34 29 2c 20 28 34 2c 20 32 ),.(1,.3),.(2,.3),.(3,.4),.(4,.2
2720 29 2c 20 28 35 2c 20 31 29 2c 20 28 35 2c 20 34 29 5d 29 0a 20 20 20 20 3e 3e 3e 20 73 65 71 75 ),.(5,.1),.(5,.4)]).....>>>.sequ
2740 65 6e 63 65 20 3d 20 28 64 20 66 6f 72 20 5f 2c 20 64 20 69 6e 20 47 2e 64 65 67 72 65 65 28 29 ence.=.(d.for._,.d.in.G.degree()
2760 29 0a 20 20 20 20 3e 3e 3e 20 6e 78 2e 69 73 5f 6d 75 6c 74 69 67 72 61 70 68 69 63 61 6c 28 73 ).....>>>.nx.is_multigraphical(s
2780 65 71 75 65 6e 63 65 29 0a 20 20 20 20 54 72 75 65 0a 0a 20 20 20 20 54 6f 20 74 65 73 74 20 61 equence).....True......To.test.a
27a0 20 6e 6f 6e 2d 6d 75 6c 74 69 67 72 61 70 68 69 63 61 6c 20 73 65 71 75 65 6e 63 65 3a 0a 20 20 .non-multigraphical.sequence:...
27c0 20 20 3e 3e 3e 20 73 65 71 75 65 6e 63 65 5f 6c 69 73 74 20 3d 20 5b 64 20 66 6f 72 20 5f 2c 20 ..>>>.sequence_list.=.[d.for._,.
27e0 64 20 69 6e 20 47 2e 64 65 67 72 65 65 28 29 5d 0a 20 20 20 20 3e 3e 3e 20 73 65 71 75 65 6e 63 d.in.G.degree()].....>>>.sequenc
2800 65 5f 6c 69 73 74 5b 2d 31 5d 20 2b 3d 20 31 0a 20 20 20 20 3e 3e 3e 20 6e 78 2e 69 73 5f 6d 75 e_list[-1].+=.1.....>>>.nx.is_mu
2820 6c 74 69 67 72 61 70 68 69 63 61 6c 28 73 65 71 75 65 6e 63 65 5f 6c 69 73 74 29 0a 20 20 20 20 ltigraphical(sequence_list).....
2840 46 61 6c 73 65 0a 0a 20 20 20 20 4e 6f 74 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 0a 20 20 20 20 54 False......Notes.....-----.....T
2860 68 65 20 77 6f 72 73 74 2d 63 61 73 65 20 72 75 6e 20 74 69 6d 65 20 69 73 20 24 4f 28 6e 29 24 he.worst-case.run.time.is.$O(n)$
2880 20 77 68 65 72 65 20 24 6e 24 20 69 73 20 74 68 65 20 6c 65 6e 67 74 68 20 6f 66 20 74 68 65 20 .where.$n$.is.the.length.of.the.
28a0 73 65 71 75 65 6e 63 65 2e 0a 0a 20 20 20 20 52 65 66 65 72 65 6e 63 65 73 0a 20 20 20 20 2d 2d sequence.......References.....--
28c0 2d 2d 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 2e 2e 20 5b 31 5d 20 53 2e 20 4c 2e 20 48 61 6b 69 6d 69 --------........[1].S..L..Hakimi
28e0 2e 20 22 4f 6e 20 74 68 65 20 72 65 61 6c 69 7a 61 62 69 6c 69 74 79 20 6f 66 20 61 20 73 65 74 .."On.the.realizability.of.a.set
2900 20 6f 66 20 69 6e 74 65 67 65 72 73 20 61 73 0a 20 20 20 20 20 20 20 64 65 67 72 65 65 73 20 6f .of.integers.as........degrees.o
2920 66 20 74 68 65 20 76 65 72 74 69 63 65 73 20 6f 66 20 61 20 6c 69 6e 65 61 72 20 67 72 61 70 68 f.the.vertices.of.a.linear.graph
2940 22 2c 20 4a 2e 20 53 49 41 4d 2c 20 31 30 2c 20 70 70 2e 20 34 39 36 2d 35 30 36 0a 20 20 20 20 ",.J..SIAM,.10,.pp..496-506.....
2960 20 20 20 28 31 39 36 32 29 2e 0a 20 20 20 20 46 a9 02 72 02 00 00 00 72 02 00 00 00 72 02 00 00 ...(1962)......F..r....r....r...
2980 00 72 18 00 00 00 54 29 05 72 0e 00 00 00 72 19 00 00 00 72 1a 00 00 00 da 0d 4e 65 74 77 6f 72 .r....T).r....r....r......Networ
29a0 6b 58 45 72 72 6f 72 72 1d 00 00 00 29 05 72 10 00 00 00 72 1f 00 00 00 72 24 00 00 00 72 22 00 kXErrorr....).r....r....r$...r".
29c0 00 00 72 26 00 00 00 73 05 00 00 00 20 20 20 20 20 72 14 00 00 00 72 04 00 00 00 72 04 00 00 00 ..r&...s.........r....r....r....
29e0 15 01 00 00 73 86 00 00 00 80 00 f0 4a 01 03 05 15 dc 17 19 97 78 91 78 d7 17 31 d1 17 31 b0 28 ....s.......J........x.x..1..1.(
2a00 d3 17 3b 88 0c f0 06 00 12 16 81 4a 80 44 88 24 d8 0d 19 f2 00 03 05 2c 88 01 d8 0b 0c 88 71 8a ..;........J.D.$.......,......q.
2a20 35 d9 13 18 d8 15 19 98 41 91 58 9c 73 a0 34 a8 11 9b 7c 88 64 89 04 f0 07 03 05 2c f0 08 00 08 5.......A.X.s.4...|.d......,....
2a40 0c 88 61 82 78 90 34 98 21 98 64 99 28 92 3f d8 0f 14 d8 0b 0f f8 f4 13 00 0c 0e d7 0b 1b d1 0b ..a.x.4.!.d.(.?.................
2a60 1b f2 00 01 05 15 d9 0f 14 f0 03 01 05 15 fa 73 11 00 00 00 82 1f 41 14 00 c1 14 13 41 2a 03 c1 ...............s......A.....A*..
2a80 29 01 41 2a 03 63 01 00 00 00 00 00 00 00 00 00 00 00 04 00 00 00 03 00 00 00 f3 b6 00 00 00 97 ).A*.c..........................
2aa0 00 09 00 74 00 00 00 00 00 00 00 00 00 6a 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ...t.........j..................
2ac0 00 6a 05 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7c 00 ab 01 00 00 00 00 00 00 7d .j...................|.........}
2ae0 01 74 09 00 00 00 00 00 00 00 00 7c 01 ab 01 00 00 00 00 00 00 64 02 7a 06 00 00 64 03 6b 28 00 .t.........|.........d.z...d.k(.
2b00 00 78 01 72 0e 01 00 74 0b 00 00 00 00 00 00 00 00 7c 01 ab 01 00 00 00 00 00 00 64 03 6b 5c 00 .x.r...t.........|.........d.k\.
2b20 00 53 00 23 00 74 00 00 00 00 00 00 00 00 00 6a 06 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 .S.#.t.........j................
2b40 00 00 00 24 00 72 03 01 00 59 00 79 01 77 00 78 03 59 00 77 01 29 04 61 3a 04 00 00 52 65 74 75 ...$.r...Y.y.w.x.Y.w.).a:...Retu
2b60 72 6e 73 20 54 72 75 65 20 69 66 20 73 6f 6d 65 20 70 73 65 75 64 6f 67 72 61 70 68 20 63 61 6e rns.True.if.some.pseudograph.can
2b80 20 72 65 61 6c 69 7a 65 20 74 68 65 20 73 65 71 75 65 6e 63 65 2e 0a 0a 20 20 20 20 45 76 65 72 .realize.the.sequence.......Ever
2ba0 79 20 6e 6f 6e 6e 65 67 61 74 69 76 65 20 69 6e 74 65 67 65 72 20 73 65 71 75 65 6e 63 65 20 77 y.nonnegative.integer.sequence.w
2bc0 69 74 68 20 61 6e 20 65 76 65 6e 20 73 75 6d 20 69 73 20 70 73 65 75 64 6f 67 72 61 70 68 69 63 ith.an.even.sum.is.pseudographic
2be0 61 6c 0a 20 20 20 20 28 73 65 65 20 5b 31 5d 5f 29 2e 0a 0a 20 20 20 20 50 61 72 61 6d 65 74 65 al.....(see.[1]_).......Paramete
2c00 72 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 73 65 71 75 65 6e 63 65 20 3a rs.....----------.....sequence.:
2c20 20 6c 69 73 74 20 6f 72 20 69 74 65 72 61 62 6c 65 20 63 6f 6e 74 61 69 6e 65 72 0a 20 20 20 20 .list.or.iterable.container.....
2c40 20 20 20 20 41 20 73 65 71 75 65 6e 63 65 20 6f 66 20 69 6e 74 65 67 65 72 20 6e 6f 64 65 20 64 ....A.sequence.of.integer.node.d
2c60 65 67 72 65 65 73 0a 0a 20 20 20 20 52 65 74 75 72 6e 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 0a egrees......Returns.....-------.
2c80 20 20 20 20 76 61 6c 69 64 20 3a 20 62 6f 6f 6c 0a 20 20 20 20 20 20 54 72 75 65 20 69 66 20 74 ....valid.:.bool.......True.if.t
2ca0 68 65 20 73 65 71 75 65 6e 63 65 20 69 73 20 61 20 70 73 65 75 64 6f 67 72 61 70 68 69 63 20 64 he.sequence.is.a.pseudographic.d
2cc0 65 67 72 65 65 20 73 65 71 75 65 6e 63 65 20 61 6e 64 20 46 61 6c 73 65 20 69 66 20 6e 6f 74 2e egree.sequence.and.False.if.not.
2ce0 0a 0a 20 20 20 20 45 78 61 6d 70 6c 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 ......Examples.....--------.....
2d00 3e 3e 3e 20 47 20 3d 20 6e 78 2e 47 72 61 70 68 28 5b 28 31 2c 20 32 29 2c 20 28 31 2c 20 33 29 >>>.G.=.nx.Graph([(1,.2),.(1,.3)
2d20 2c 20 28 32 2c 20 33 29 2c 20 28 33 2c 20 34 29 2c 20 28 34 2c 20 32 29 2c 20 28 35 2c 20 31 29 ,.(2,.3),.(3,.4),.(4,.2),.(5,.1)
2d40 2c 20 28 35 2c 20 34 29 5d 29 0a 20 20 20 20 3e 3e 3e 20 73 65 71 75 65 6e 63 65 20 3d 20 28 64 ,.(5,.4)]).....>>>.sequence.=.(d
2d60 20 66 6f 72 20 5f 2c 20 64 20 69 6e 20 47 2e 64 65 67 72 65 65 28 29 29 0a 20 20 20 20 3e 3e 3e .for._,.d.in.G.degree()).....>>>
2d80 20 6e 78 2e 69 73 5f 70 73 65 75 64 6f 67 72 61 70 68 69 63 61 6c 28 73 65 71 75 65 6e 63 65 29 .nx.is_pseudographical(sequence)
2da0 0a 20 20 20 20 54 72 75 65 0a 0a 20 20 20 20 54 6f 20 74 65 73 74 20 61 20 6e 6f 6e 2d 70 73 65 .....True......To.test.a.non-pse
2dc0 75 64 6f 67 72 61 70 68 69 63 61 6c 20 73 65 71 75 65 6e 63 65 3a 0a 20 20 20 20 3e 3e 3e 20 73 udographical.sequence:.....>>>.s
2de0 65 71 75 65 6e 63 65 5f 6c 69 73 74 20 3d 20 5b 64 20 66 6f 72 20 5f 2c 20 64 20 69 6e 20 47 2e equence_list.=.[d.for._,.d.in.G.
2e00 64 65 67 72 65 65 28 29 5d 0a 20 20 20 20 3e 3e 3e 20 73 65 71 75 65 6e 63 65 5f 6c 69 73 74 5b degree()].....>>>.sequence_list[
2e20 2d 31 5d 20 2b 3d 20 31 0a 20 20 20 20 3e 3e 3e 20 6e 78 2e 69 73 5f 70 73 65 75 64 6f 67 72 61 -1].+=.1.....>>>.nx.is_pseudogra
2e40 70 68 69 63 61 6c 28 73 65 71 75 65 6e 63 65 5f 6c 69 73 74 29 0a 20 20 20 20 46 61 6c 73 65 0a phical(sequence_list).....False.
2e60 0a 20 20 20 20 4e 6f 74 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 0a 20 20 20 20 54 68 65 20 77 6f 72 .....Notes.....-----.....The.wor
2e80 73 74 2d 63 61 73 65 20 72 75 6e 20 74 69 6d 65 20 69 73 20 24 4f 28 6e 29 24 20 77 68 65 72 65 st-case.run.time.is.$O(n)$.where
2ea0 20 6e 20 69 73 20 74 68 65 20 6c 65 6e 67 74 68 20 6f 66 20 74 68 65 20 73 65 71 75 65 6e 63 65 .n.is.the.length.of.the.sequence
2ec0 2e 0a 0a 20 20 20 20 52 65 66 65 72 65 6e 63 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d .......References.....----------
2ee0 0a 20 20 20 20 2e 2e 20 5b 31 5d 20 46 2e 20 42 6f 65 73 63 68 20 61 6e 64 20 46 2e 20 48 61 72 ........[1].F..Boesch.and.F..Har
2f00 61 72 79 2e 20 22 4c 69 6e 65 20 72 65 6d 6f 76 61 6c 20 61 6c 67 6f 72 69 74 68 6d 73 20 66 6f ary.."Line.removal.algorithms.fo
2f20 72 20 67 72 61 70 68 73 0a 20 20 20 20 20 20 20 61 6e 64 20 74 68 65 69 72 20 64 65 67 72 65 65 r.graphs........and.their.degree
2f40 20 6c 69 73 74 73 22 2c 20 49 45 45 45 20 54 72 61 6e 73 2e 20 43 69 72 63 75 69 74 73 20 61 6e .lists",.IEEE.Trans..Circuits.an
2f60 64 20 53 79 73 74 65 6d 73 2c 20 43 41 53 2d 32 33 28 31 32 29 2c 0a 20 20 20 20 20 20 20 70 70 d.Systems,.CAS-23(12),........pp
2f80 2e 20 37 37 38 2d 37 38 32 20 28 31 39 37 36 29 2e 0a 20 20 20 20 46 72 18 00 00 00 72 02 00 00 ..778-782.(1976)......Fr....r...
2fa0 00 29 06 72 0e 00 00 00 72 19 00 00 00 72 1a 00 00 00 72 3b 00 00 00 da 03 73 75 6d 72 1e 00 00 .).r....r....r....r;.....sumr...
2fc0 00 29 02 72 10 00 00 00 72 1f 00 00 00 73 02 00 00 00 20 20 72 14 00 00 00 72 05 00 00 00 72 05 .).r....r....s......r....r....r.
2fe0 00 00 00 48 01 00 00 73 5c 00 00 00 80 00 f0 50 01 03 05 15 dc 17 19 97 78 91 78 d7 17 31 d1 17 ...H...s\......P........x.x..1..
3000 31 b0 28 d3 17 3b 88 0c f4 06 00 0c 0f 88 7c d3 0b 1c 98 71 d1 0b 20 a0 41 d1 0b 25 d2 0b 40 ac 1.(..;........|....q....A..%..@.
3020 23 a8 6c d3 2a 3b b8 71 d1 2a 40 d0 04 40 f8 f4 05 00 0c 0e d7 0b 1b d1 0b 1b f2 00 01 05 15 d9 #.l.*;.q.*@..@..................
3040 0f 14 f0 03 01 05 15 fa 73 11 00 00 00 82 1f 41 02 00 c1 02 13 41 18 03 c1 17 01 41 18 03 63 02 ........s......A.....A.....A..c.
3060 00 00 00 00 00 00 00 00 00 00 00 07 00 00 00 03 00 00 00 f3 d6 04 00 00 97 00 09 00 74 00 00 00 ............................t...
3080 00 00 00 00 00 00 6a 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 6a 05 00 00 00 00 ......j...................j.....
30a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7c 00 ab 01 00 00 00 00 00 00 7d 02 74 00 00 00 00 00 ..............|.........}.t.....
30c0 00 00 00 00 6a 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 6a 05 00 00 00 00 00 00 ....j...................j.......
30e0 00 00 00 00 00 00 00 00 00 00 00 00 7c 01 ab 01 00 00 00 00 00 00 7d 03 64 02 64 02 74 09 00 00 ............|.........}.d.d.t...
3100 00 00 00 00 00 00 7c 02 ab 01 00 00 00 00 00 00 74 09 00 00 00 00 00 00 00 00 7c 03 ab 01 00 00 ......|.........t.........|.....
3120 00 00 00 00 66 04 5c 04 00 00 7d 04 7d 05 7d 06 7d 07 74 0b 00 00 00 00 00 00 00 00 7c 06 7c 07 ....f.\...}.}.}.}.t.........|.|.
3140 ab 02 00 00 00 00 00 00 7d 08 64 02 7d 09 7c 08 64 02 6b 28 00 00 72 01 79 03 67 00 67 00 7d 0b ........}.d.}.|.d.k(..r.y.g.g.}.
3160 7d 0a 74 0d 00 00 00 00 00 00 00 00 7c 08 ab 01 00 00 00 00 00 00 44 00 5d 76 00 00 7d 0c 64 04 }.t.........|.........D.]v..}.d.
3180 5c 02 00 00 7d 0d 7d 0e 7c 0c 7c 07 6b 02 00 00 72 05 7c 03 7c 0c 19 00 00 00 7d 0e 7c 0c 7c 06 \...}.}.|.|.k...r.|.|.....}.|.|.
31a0 6b 02 00 00 72 05 7c 02 7c 0c 19 00 00 00 7d 0d 7c 0d 64 02 6b 02 00 00 73 05 7c 0e 64 02 6b 02 k...r.|.|.....}.|.d.k...s.|.d.k.
31c0 00 00 72 02 01 00 79 01 7c 04 7c 0d 7a 00 00 00 7c 05 7c 0e 7a 00 00 00 74 0b 00 00 00 00 00 00 ..r...y.|.|.z...|.|.z...t.......
31e0 00 00 7c 09 7c 0d ab 02 00 00 00 00 00 00 7d 09 7d 05 7d 04 7c 0d 64 02 6b 44 00 00 72 1a 7c 0a ..|.|.........}.}.}.|.d.kD..r.|.
3200 6a 0f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 64 05 7c 0e 7a 05 00 00 64 05 7c 0d j...................d.|.z...d.|.
3220 7a 05 00 00 66 02 ab 01 00 00 00 00 00 00 01 00 8c 5d 7c 0e 64 02 6b 44 00 00 73 01 8c 63 7c 0b z...f............]|.d.kD..s..c|.
3240 6a 0f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 64 05 7c 0e 7a 05 00 00 ab 01 00 00 j...................d.|.z.......
3260 00 00 00 00 01 00 8c 78 04 00 7c 04 7c 05 6b 37 00 00 72 01 79 01 74 11 00 00 00 00 00 00 00 00 .......x..|.|.k7..r.y.t.........
3280 6a 12 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7c 0a ab 01 00 00 00 00 00 00 01 00 j...................|...........
32a0 74 11 00 00 00 00 00 00 00 00 6a 12 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7c 0b t.........j...................|.
32c0 ab 01 00 00 00 00 00 00 01 00 64 04 67 01 7c 09 64 06 7a 00 00 00 7a 05 00 00 7d 0f 7c 0a 90 01 ..........d.g.|.d.z...z...}.|...
32e0 72 1c 74 11 00 00 00 00 00 00 00 00 6a 14 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r.t.........j...................
3300 7c 0a ab 01 00 00 00 00 00 00 5c 02 00 00 7d 10 7d 11 7c 11 64 05 7a 12 00 00 7d 11 7c 11 74 09 |.........\...}.}.|.d.z...}.|.t.
3320 00 00 00 00 00 00 00 00 7c 0a ab 01 00 00 00 00 00 00 74 09 00 00 00 00 00 00 00 00 7c 0b ab 01 ........|.........t.........|...
3340 00 00 00 00 00 00 7a 00 00 00 6b 44 00 00 72 01 79 01 64 02 7d 12 74 0d 00 00 00 00 00 00 00 00 ......z...kD..r.y.d.}.t.........
3360 7c 11 ab 01 00 00 00 00 00 00 44 00 5d 68 00 00 7d 13 7c 0b 72 28 7c 0a 72 0e 7c 0a 64 02 19 00 |.........D.]h..}.|.r(|.r.|.d...
3380 00 00 64 02 19 00 00 00 7c 0b 64 02 19 00 00 00 6b 44 00 00 72 18 74 11 00 00 00 00 00 00 00 00 ..d.....|.d.....kD..r.t.........
33a0 6a 14 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7c 0b ab 01 00 00 00 00 00 00 7d 14 j...................|.........}.
33c0 64 02 7d 15 6e 18 74 11 00 00 00 00 00 00 00 00 6a 14 00 00 00 00 00 00 00 00 00 00 00 00 00 00 d.}.n.t.........j...............
33e0 00 00 00 00 7c 0a ab 01 00 00 00 00 00 00 5c 02 00 00 7d 14 7d 15 7c 14 64 02 6b 28 00 00 72 02 ....|.........\...}.}.|.d.k(..r.
3400 01 00 79 01 7c 14 64 06 7a 00 00 00 64 02 6b 02 00 00 73 06 7c 15 64 02 6b 02 00 00 73 01 8c 5a ..y.|.d.z...d.k...s.|.d.k...s..Z
3420 7c 14 64 06 7a 00 00 00 7c 15 66 02 7c 0f 7c 12 3c 00 00 00 7c 12 64 06 7a 0d 00 00 7d 12 8c 6a |.d.z...|.f.|.|.<...|.d.z...}..j
3440 04 00 74 0d 00 00 00 00 00 00 00 00 7c 12 ab 01 00 00 00 00 00 00 44 00 5d 3f 00 00 7d 13 7c 0f ..t.........|.........D.]?..}.|.
3460 7c 13 19 00 00 00 7d 16 7c 16 64 06 19 00 00 00 64 02 6b 02 00 00 72 17 74 11 00 00 00 00 00 00 |.....}.|.d.....d.k...r.t.......
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34c0 00 00 00 00 7c 0b 7c 16 64 02 19 00 00 00 ab 02 00 00 00 00 00 00 01 00 8c 41 04 00 7c 10 64 02 ....|.|.d................A..|.d.
34e0 6b 02 00 00 72 16 74 11 00 00 00 00 00 00 00 00 6a 16 00 00 00 00 00 00 00 00 00 00 00 00 00 00 k...r.t.........j...............
3500 00 00 00 00 7c 0b 7c 10 ab 02 00 00 00 00 00 00 01 00 7c 0a 72 02 90 01 8c 1c 79 03 23 00 74 00 ....|.|...........|.r.....y.#.t.
3520 00 00 00 00 00 00 00 00 6a 06 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 24 00 72 03 ........j...................$.r.
3540 01 00 59 00 79 01 77 00 78 03 59 00 77 01 29 07 61 e8 04 00 00 52 65 74 75 72 6e 73 20 54 72 75 ..Y.y.w.x.Y.w.).a....Returns.Tru
3560 65 20 69 66 20 73 6f 6d 65 20 64 69 72 65 63 74 65 64 20 67 72 61 70 68 20 63 61 6e 20 72 65 61 e.if.some.directed.graph.can.rea
3580 6c 69 7a 65 20 74 68 65 20 69 6e 2d 20 61 6e 64 20 6f 75 74 2d 64 65 67 72 65 65 0a 20 20 20 20 lize.the.in-.and.out-degree.....
35a0 73 65 71 75 65 6e 63 65 73 2e 0a 0a 20 20 20 20 50 61 72 61 6d 65 74 65 72 73 0a 20 20 20 20 2d sequences.......Parameters.....-
35c0 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 69 6e 5f 73 65 71 75 65 6e 63 65 20 3a 20 6c 69 73 74 ---------.....in_sequence.:.list
35e0 20 6f 72 20 69 74 65 72 61 62 6c 65 20 63 6f 6e 74 61 69 6e 65 72 0a 20 20 20 20 20 20 20 20 41 .or.iterable.container.........A
3600 20 73 65 71 75 65 6e 63 65 20 6f 66 20 69 6e 74 65 67 65 72 20 6e 6f 64 65 20 69 6e 2d 64 65 67 .sequence.of.integer.node.in-deg
3620 72 65 65 73 0a 0a 20 20 20 20 6f 75 74 5f 73 65 71 75 65 6e 63 65 20 3a 20 6c 69 73 74 20 6f 72 rees......out_sequence.:.list.or
3640 20 69 74 65 72 61 62 6c 65 20 63 6f 6e 74 61 69 6e 65 72 0a 20 20 20 20 20 20 20 20 41 20 73 65 .iterable.container.........A.se
3660 71 75 65 6e 63 65 20 6f 66 20 69 6e 74 65 67 65 72 20 6e 6f 64 65 20 6f 75 74 2d 64 65 67 72 65 quence.of.integer.node.out-degre
3680 65 73 0a 0a 20 20 20 20 52 65 74 75 72 6e 73 0a 20 20 20 20 2d 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 es......Returns.....-------.....
36a0 76 61 6c 69 64 20 3a 20 62 6f 6f 6c 0a 20 20 20 20 20 20 54 72 75 65 20 69 66 20 69 6e 20 61 6e valid.:.bool.......True.if.in.an
36c0 64 20 6f 75 74 2d 73 65 71 75 65 6e 63 65 73 20 61 72 65 20 64 69 67 72 61 70 68 69 63 20 46 61 d.out-sequences.are.digraphic.Fa
36e0 6c 73 65 20 69 66 20 6e 6f 74 2e 0a 0a 20 20 20 20 45 78 61 6d 70 6c 65 73 0a 20 20 20 20 2d 2d lse.if.not.......Examples.....--
3700 2d 2d 2d 2d 2d 2d 0a 20 20 20 20 3e 3e 3e 20 47 20 3d 20 6e 78 2e 44 69 47 72 61 70 68 28 5b 28 ------.....>>>.G.=.nx.DiGraph([(
3720 31 2c 20 32 29 2c 20 28 31 2c 20 33 29 2c 20 28 32 2c 20 33 29 2c 20 28 33 2c 20 34 29 2c 20 28 1,.2),.(1,.3),.(2,.3),.(3,.4),.(
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3760 69 6e 5f 73 65 71 20 3d 20 28 64 20 66 6f 72 20 6e 2c 20 64 20 69 6e 20 47 2e 69 6e 5f 64 65 67 in_seq.=.(d.for.n,.d.in.G.in_deg
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37a0 6e 2c 20 64 20 69 6e 20 47 2e 6f 75 74 5f 64 65 67 72 65 65 28 29 29 0a 20 20 20 20 3e 3e 3e 20 n,.d.in.G.out_degree()).....>>>.
37c0 6e 78 2e 69 73 5f 64 69 67 72 61 70 68 69 63 61 6c 28 69 6e 5f 73 65 71 2c 20 6f 75 74 5f 73 65 nx.is_digraphical(in_seq,.out_se
37e0 71 29 0a 20 20 20 20 54 72 75 65 0a 0a 20 20 20 20 54 6f 20 74 65 73 74 20 61 20 6e 6f 6e 2d 64 q).....True......To.test.a.non-d
3800 69 67 72 61 70 68 69 63 61 6c 20 73 63 65 6e 61 72 69 6f 3a 0a 20 20 20 20 3e 3e 3e 20 69 6e 5f igraphical.scenario:.....>>>.in_
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3840 65 67 72 65 65 28 29 5d 0a 20 20 20 20 3e 3e 3e 20 69 6e 5f 73 65 71 5f 6c 69 73 74 5b 2d 31 5d egree()].....>>>.in_seq_list[-1]
3860 20 2b 3d 20 31 0a 20 20 20 20 3e 3e 3e 20 6e 78 2e 69 73 5f 64 69 67 72 61 70 68 69 63 61 6c 28 .+=.1.....>>>.nx.is_digraphical(
3880 69 6e 5f 73 65 71 5f 6c 69 73 74 2c 20 6f 75 74 5f 73 65 71 29 0a 20 20 20 20 46 61 6c 73 65 0a in_seq_list,.out_seq).....False.
38a0 0a 20 20 20 20 4e 6f 74 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d 0a 20 20 20 20 54 68 69 73 20 61 6c .....Notes.....-----.....This.al
38c0 67 6f 72 69 74 68 6d 20 69 73 20 66 72 6f 6d 20 4b 6c 65 69 74 6d 61 6e 20 61 6e 64 20 57 61 6e gorithm.is.from.Kleitman.and.Wan
38e0 67 20 5b 31 5d 5f 2e 0a 20 20 20 20 54 68 65 20 77 6f 72 73 74 20 63 61 73 65 20 72 75 6e 74 69 g.[1]_......The.worst.case.runti
3900 6d 65 20 69 73 20 24 4f 28 73 20 5c 74 69 6d 65 73 20 5c 6c 6f 67 20 6e 29 24 20 77 68 65 72 65 me.is.$O(s.\times.\log.n)$.where
3920 20 24 73 24 20 61 6e 64 20 24 6e 24 20 61 72 65 20 74 68 65 0a 20 20 20 20 73 75 6d 20 61 6e 64 .$s$.and.$n$.are.the.....sum.and
3940 20 6c 65 6e 67 74 68 20 6f 66 20 74 68 65 20 73 65 71 75 65 6e 63 65 73 20 72 65 73 70 65 63 74 .length.of.the.sequences.respect
3960 69 76 65 6c 79 2e 0a 0a 20 20 20 20 52 65 66 65 72 65 6e 63 65 73 0a 20 20 20 20 2d 2d 2d 2d 2d ively.......References.....-----
3980 2d 2d 2d 2d 2d 0a 20 20 20 20 2e 2e 20 5b 31 5d 20 44 2e 4a 2e 20 4b 6c 65 69 74 6d 61 6e 20 61 -----........[1].D.J..Kleitman.a
39a0 6e 64 20 44 2e 4c 2e 20 57 61 6e 67 0a 20 20 20 20 20 20 20 41 6c 67 6f 72 69 74 68 6d 73 20 66 nd.D.L..Wang........Algorithms.f
39c0 6f 72 20 43 6f 6e 73 74 72 75 63 74 69 6e 67 20 47 72 61 70 68 73 20 61 6e 64 20 44 69 67 72 61 or.Constructing.Graphs.and.Digra
39e0 70 68 73 20 77 69 74 68 20 47 69 76 65 6e 20 56 61 6c 65 6e 63 65 73 0a 20 20 20 20 20 20 20 61 phs.with.Given.Valences........a
3a00 6e 64 20 46 61 63 74 6f 72 73 2c 20 44 69 73 63 72 65 74 65 20 4d 61 74 68 65 6d 61 74 69 63 73 nd.Factors,.Discrete.Mathematics
3a20 2c 20 36 28 31 29 2c 20 70 70 2e 20 37 39 2d 38 38 20 28 31 39 37 33 29 0a 20 20 20 20 46 72 02 ,.6(1),.pp..79-88.(1973).....Fr.
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3ae0 6e 63 65 da 05 73 75 6d 69 6e da 06 73 75 6d 6f 75 74 da 03 6e 69 6e da 04 6e 6f 75 74 da 04 6d nce..sumin..sumout..nin..nout..m
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3b60 74 75 62 69 6e 72 30 00 00 00 73 17 00 00 00 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 tubinr0...s.....................
3b80 20 20 20 20 20 20 72 14 00 00 00 72 06 00 00 00 72 06 00 00 00 77 01 00 00 73 98 02 00 00 80 00 ......r....r....r....w...s......
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3be0 3f 4f d3 3b 50 d0 1f 50 d1 04 1c 80 45 88 36 90 33 98 04 dc 0b 0e 88 73 90 44 8b 3e 80 44 d8 0c ?O.;P..P....E.6.3......s.D.>.D..
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3dc0 41 d8 13 1b 98 41 91 3b 88 44 d8 0f 13 90 41 89 77 98 11 8a 7b dc 10 15 97 0e 91 0e 98 78 a8 14 A....A.;.D....A.w...{........x..
3de0 d5 10 2e e4 10 15 97 0e 91 0e 98 78 a8 14 a8 61 a9 17 d5 10 31 f0 0b 05 09 32 f0 0c 00 0c 13 90 ...........x...a....1....2......
3e00 51 8a 3b dc 0c 11 8f 4e 89 4e 98 38 a0 57 d4 0c 2d f3 3d 00 0b 13 f0 3e 00 0c 10 f8 f4 7b 01 00 Q.;....N.N.8.W..-.=....>.....{..
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