【无聊放个模板系列】HDU 1269 (SCC)

 1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<cstring>
 4 #include<iostream>
 5 #include<algorithm>
 6 #include<queue>
 7 #include<cmath>
 8 #include<stack>
 9 using namespace std;
10 #define Maxn 10010
11 #define Maxm 100010
12 
13 struct node
14 {
15     int x,y,next;
16 }t[Maxm];int len;
17 int first[Maxn];
18 
19 void ins(int x,int y)
20 {
21     t[++len].x=x;t[len].y=y;
22     t[len].next=first[x];first[x]=len;
23 }
24 
25 int mymin(int x,int y) {return x<y?x:y;}
26 
27 int dfn[Maxn],low[Maxn],cnt,scc;
28 stack<int > s;
29 bool inst[Maxn];
30 
31 void dfs(int x,int f)
32 {
33     dfn[x]=low[x]=++cnt;
34     inst[x]=1;s.push(x);
35     for(int i=first[x];i;i=t[i].next) if(t[i].y!=f)
36     {
37         int y=t[i].y;
38         if(dfn[y]==0)
39         {
40             dfs(y,x);
41             low[x]=mymin(low[x],low[y]);
42         }
43         else if(inst[y]) low[x]=mymin(low[x],dfn[y]);
44     }
45     if(low[x]==dfn[x])
46     {
47         int z;scc++;
48         while(1)
49         {
50             z=s.top();s.pop();
51             inst[z]=0;
52             if(z==x) break;
53         }
54     }
55 }
56 
57 int main()
58 {
59     while(1)
60     {
61         int n,m;
62         scanf("%d%d",&n,&m);
63         if(n==0&&m==0) break;
64         len=0;
65         memset(first,0,sizeof(first));
66         for(int i=1;i<=m;i++)
67         {
68             int x,y;
69             scanf("%d%d",&x,&y);
70             ins(x,y);
71         }
72         cnt=0;scc=0;
73         memset(dfn,0,sizeof(dfn));
74         memset(inst,0,sizeof(inst));
75         for(int i=1;i<=n;i++) if(dfn[i]==0) dfs(i,0);
76         if(scc==1) printf("Yes\n");
77         else printf("No\n");
78     }
79     return 0;
80 }

 

SCC

 

2016-11-17 20:56:27

posted @ 2016-11-17 20:51  konjak魔芋  阅读(200)  评论(0编辑  收藏  举报