Zju1311 network-undirected graph cut point

Question:

Returns an undirected graph and calculates the number of cut points in the graph. (If vertex I and its adjacent edges are removed, the remaining graph is not connected, Then I is the cut point)

Analysis:

There is a mature DFS Algorithm for Finding cut points. One is written as a backup template.

 

1. /*
2. Zju1311 Network
3. */
5. # Include <stdio. h>
6. # Include <memory. h>
8. # Define CLR (a) memset (A, 0, sizeof ())
9. # Define min (A, B) (a)> (B )? (B) ())
10. # Define N 105
12. Int N;
13. Int a [n] [N];
14. Int cut [N];
16. Char * Next (char STR [], char * SP ){
17. While (* sp & * SP! = '') SP ++;
18. While (* sp & * sp = '') SP ++;
19. Return sp;
20. }
22. /**************************************/
24. Int ancestor [N];
25. Int mark [N];
26. Int deep [N];
28. Int DFS (int I, int father, int dth, int B [] [N], int cut []) {
29. Int j, k, sons = 0, count = 0;
30. Mark [I] = 1;
31. Deep [I] = ancestor [I] = dth;
32. For (k = B [I] [0]; k> = 1; k --){
33. J = B [I] [k];
34. If (j! = Father & mark [j] = 1) ancestor [I] = MIN (ancestor [I], deep [j]);
35. If (mark [j] = 0 ){
36. Count + = DFS (j, I, dth + 1, B, cut );
37. Sons ++;
38. Ancestor [I] = min (ancestor [I], ancestor [J]);
39. If (Father =-1 & Sons> 1) | (father! =-1 & ancestor [J]> = deep [I])
40. Cut [I] = 1;
41. // If (ancestor [J]> deep [I]) brige [I] [J] = 1;
42. }
43. }
44. Mark [I] = 2;
45. Return count + cut [I];
46. }
47. /*
48. Cut Point
49. Parameter: A [] [] adjacent matrix. Non-0 represents connectivity. N.
50. Return: Number of cut points. Cut [I] = 1 indicates that I is a cut point.
51. Note: The DFS algorithm first converts the adjacent matrix into an adjacent table to handle the situation where the graph itself is not connected. Complexity O (E)
52. The bridge where the image can be modified.
53. */
54. Int cutpoints (int A [] [N], int N, int cut []) {
55. Int I, j, B [N] [N], Count = 0;
56. For (I = 0; I <n; I ++) Cut [I] = B [I] [0] = 0;
57. Memset (mark, 0, sizeof (Mark ));
58. For (I = 0; I <n; I ++) for (j = 0; j <n; j ++) if (a [I] [J]) B [I] [++ B [I] [0] = J;
59. For (I = 0; I <n; I ++) if (MARK [I] = 0) Count + = DFS (0,-1, 0, B, cut );
60. Return count;
61. }
63. /**************************************/
65. Int main ()
66. {
67. Int I, J, K;
68. Char STR [N * 10], * sp;
70. While (scanf ("% d", & N )! = EOF & N ){
71. // Init
72. CLR ();
73. // Input
74. While (scanf ("% d", & I), I ){
75. Gets (STR );
76. For (sp = next (STR, STR); sscanf (SP, "% d", & J )! = EOF; SP = next (STR, SP )){
77. A [I-1] [J-1] = A [J-1] [I-1] = 1;
78. }
79. }
80. // Work
81. Printf ("% d/N", cutpoints (A, N, cut ));
82. }
84. Return 0;
85. }