HDU 1269 迷宫城堡(Tarjan算法)

Tarjan算法模版求强连通分量。

 1 #include <iostream>

 2 #include <cstring>

 3 #include <cstdio>

 4 #include <cstdlib>

 5 using namespace std;

 6 #define N 10000

 7 #define M 100000

 8 struct node

 9 {

10     int u,v,next;

11 }edge[M+10];

12 int t,top,scnt;

13 int DFN[N+1],Low[N+1],Belong[N+1],stack[N+1],first[N+1];

14 int in[N+1];

15 void CL()

16 {

17     t = 0;

18     t = scnt = top = 0;

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

20     memset(DFN,0,sizeof(DFN));

21 }

22 void add(int u,int v)

23 {

24     edge[t].u = u;

25     edge[t].v = v;

26     edge[t].next = first[u];

27     first[u] = t ++;

28 }

29 void Tarjan(int u)

30 {

31     int v,i;

32     DFN[u] = Low[u] = ++ t;

33     in[u] = 1;

34     stack[top++] = u;

35     for(i = first[u];i != -1;i = edge[i].next)

36     {

37         v = edge[i].v;

38         if(!DFN[v])

39         {

40             Tarjan(v);

41             if(Low[u] > Low[v])

42             {

43                 Low[u] = Low[v];

44             }

45         }

46         else if(in[v] && Low[u] > DFN[v])

47         {

48             Low[u] = DFN[v];

49         }

50     }

51     if(DFN[u] == Low[u])

52     {

53         scnt ++;

54         do

55         {

56             v = stack[--top];

57             in[v] = 0;

58             Belong[v] = scnt;

59         }while(u != v);

60     }

61 }

62 int main()

63 {

64     int n,m,sv,ev,i;

65     while(scanf("%d%d",&n,&m)!=EOF)

66     {

67         if(n == 0&&m == 0)

68         break;

69         CL();

70         for(i = 1;i <= m;i ++)

71         {

72             scanf("%d%d",&sv,&ev);

73             add(sv,ev);

74         }

75         t = 0;

76         for(i = 1;i <= n;i ++)

77         {

78             if(!DFN[i])

79             {

80                 Tarjan(i);

81             }

82         }

83         if(scnt == 1)

84         printf("Yes\n");

85         else

86         printf("No\n");

87     }

88     return 0;

89 }