Tarjan+模板

 1 #include<stdio.h>

 2 #include<string.h>

 3 #include<stdlib.h>

 4 #include<math.h>

 5 #include<algorithm>

 6 #include<iostream>

 7 #include<set>

 8 #include<stack>

 9 #include<queue>

10 #include<map>

11 #include<vector>

12 using namespace std;

13 

14 const int maxn = 105;

15 const int maxm = 1005;

16 const int inf = 0x3f3f3f3f;

17 const double pi = acos(-1.0);

18 const double eps = 1e-8;

19 

20 struct Edge{

21     int u,v,next;

22 }edge[ maxn*maxn ];

23 int cnt,head[ maxn ];

24 int vis[ maxn ],belong[ maxn ];

25 stack<int>s;

26 int dfn[ maxn ],low[ maxn ];

27 int Cnt ,id ;

28 

29 void init(){

30     while( !s.empty() )

31         s.pop();

32     Cnt = 0;

33     id = 0;

34     memset( dfn,-1,sizeof( dfn ) );

35     memset( low,-1,sizeof( low ) );

36     cnt = 0;

37     memset( head,-1,sizeof( head ) );

38 }

39 

40 void addedge( int a,int b ){

41     edge[ cnt ].u = a;

42     edge[ cnt ].v = b;

43     edge[ cnt ].next = head[ a ];

44     head[ a ] = cnt++;

45 }

46 

47 void tarjan( int cur ){

48     dfn[ cur ] = low[ cur ] = id++;

49     vis[ cur ] = 1;

50     s.push( cur );

51     for( int i=head[ cur ];i!=-1;i=edge[i].next ){

52         int nxt = edge[i].v;

53         if( dfn[ nxt ]==-1 ){

54             tarjan( nxt );

55             low[ cur ] = min( low[ nxt ],low[ cur ] );

56         }

57         else if( vis[ nxt ]==1 ){

58             low[ cur ] = min( dfn[ nxt ],low[ cur ] );

59         }

60     }

61     if( dfn[ cur ]==low[ cur ] ){

62         Cnt ++;

63         while( 1 ){

64             int tmp = s.top();

65             s.pop();

66             vis[ tmp ] = 0;

67             belong[ tmp ] = Cnt;

68             if( tmp==cur ) break;

69         }

70     }

71 }

72 

73 int main(){

74     int n,m;

75     while( scanf("%d%d",&n,&m)==2 ){

76         int a,b;

77         init();

78         while( m-- ){

79             scanf("%d%d",&a,&b);

80             addedge( a,b );

81         }

82         for( int i=1;i<=n;i++ ){

83             if( dfn[i]==-1 ){

84                 tarjan( i );

85             }

86         }

87         printf("缩点 = %d\n",Cnt);

88     }

89     return 0;

90 }

View Code