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#include<cstdio>#include<cstring>#include<iostream>#include<cstring>#include<vector>#include<stack>#include<algorithm>using namespace std;#define N 10003int dfn[N],low[N],ins[N],Time,num;//ins是否在栈里vector<int>gra[N];stack<int>sta;void Tarjan(int s){ dfn[s] = low[s] = ++Time; sta.push(s); ins[s] = 1; for(int i=0;i<gra[s].size();i++) { int k = gra[s][i]; if(dfn[k] == 0){ Tarjan(k); low[s] = min(low[s] ,low[k]); } if(dfn[k] != 0 && ins[k] == 1){ low[s] = min(low[s] ,dfn[k]);//low[s] = min(low[s] ,low[k]);好像也是对的 } } if(dfn[s] == low[s]) { num++; while(!sta.empty()) { int temp = sta.top(); sta.pop(); ins[temp] = 0; if(temp == s) break; } }}int main(){ int n,m; while(scanf("%d%d",&n,&m)&&(n + m)) { memset(dfn,0,sizeof(dfn)); memset(ins,0,sizeof(ins)); memset(low,0,sizeof(low)); while(!sta.empty()) sta.pop(); for(int i=1;i<=n;i++) gra[i].clear(); int a,b; while(m--) { scanf("%d%d",&a,&b); gra[a].push_back(b); } num = Time = 0; for(int i=1;i<=n;i++) { if(dfn[i]==0) Tarjan(i); } if(num > 1) printf("No\n"); else printf("Yes\n"); }} |
HDU1269迷宫城堡(裸Tarjan有向图求强连通分量个数)
原文：http://www.cnblogs.com/liwenchi/p/7259327.html