poj 1236 Network of Schools

强联通分量模版题，tarjan算法：

 1 #include<stdio.h>

 2 #include<string.h>

 3 #define MAXN 110

 4 

 5 int n, p, ans1, ans2, u[MAXN*MAXN], v[MAXN*MAXN], next[MAXN*MAXN], first[MAXN];

 6 int dfn[MAXN], low[MAXN], col[MAXN], stk[MAXN], ins[MAXN], ind, top, cols, tmp;

 7 int indg[MAXN], outdg[MAXN], zeroin, zeroout;

 8 

 9 void dfs(int u)

10 {

11     dfn[u] = low[u] = ++ind;

12     stk[++top] = u, ins[u] = 1;

13     for(int i = first[u]; i != -1; i = next[i])

14     {

15         int ve = v[i];

16         if(!dfn[ve])

17         {

18             dfs(ve);

19             if(low[ve] < low[u]) low[u] = low[ve];

20         }

21         else if(ins[ve])

22         {

23             if(dfn[ve] < low[u]) low[u] = dfn[ve];

24         }

25     }

26     if(dfn[u] == low[u])

27     {

28         cols ++;

29         do

30         {

31             tmp = stk[top--];

32             col[tmp] = cols;

33             ins[tmp] = 0;

34         }

35         while(tmp != u);

36     }

37 }

38 

39 void tarjan(int n)

40 {

41     memset(dfn, 0, sizeof(dfn));

42     memset(low, 0, sizeof(low));

43     memset(col, 0, sizeof(col));

44     memset(stk, 0, sizeof(stk));

45     memset(ins, 0, sizeof(ins));

46     ind = top = cols = 0;

47     for(int i = 1; i <= n; i ++)

48     {

49         if(!dfn[i]) dfs(i);

50     }    

51     if(cols == 1)

52     {

53         ans1 = 1, ans2 = 0;

54         return;

55     }

56     ans1 = ans2 = zeroin = zeroout = 0;

57     memset(indg, 0, sizeof(indg));

58     memset(outdg, 0, sizeof(outdg));

59     for(int u = 1; u <= n; u ++)

60     {

61         for(int i = first[u]; i != -1; i = next[i])

62         {

63             int ve = v[i];

64             if(col[u] == col[ve]) continue;

65             indg[col[ve]] ++;

66             outdg[col[u]] ++;

67         }

68     }

69     for(int i = 1; i <= cols; i ++)

70     {

71         if(indg[i] == 0) zeroin ++;

72         if(outdg[i] == 0) zeroout ++;

73     }

74     ans1 = zeroin;

75     ans2 = zeroin > zeroout ? zeroin : zeroout;

76 }

77 

78 int main()

79 {

80     while(~scanf("%d",&n))

81     {

82         memset(first, -1, sizeof(first));

83         p = 0;

84         for(int i = 1; i <= n; i ++)

85             while(1)

86             {

87                 int a;

88                 scanf("%d",&a);

89                 if(a == 0) break;

90                 u[p] = i; v[p] = a;

91                 next[p] = first[u[p]];

92                 first[u[p]] = p;

93                 p ++;

94             }

95             tarjan(n);

96             printf("%d\n%d\n",ans1, ans2);

97     }

98     return 0;

99 }