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 }

 

posted @ 2013-03-31 15:27  Naix_x  阅读(220)  评论(0)  编辑  收藏  举报