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多与DAG上的DP之类的问题一起出现。
using namespace std; const int MAXE = 300010; const int MAXP = 100010; struct N { int v,next; }edge[MAXE]; int head[MAXP]; int Top; int ty[MAXP]; int high[MAXP]; int lowlink[MAXP]; int SCCans,dfsclock; int S[MAXP],STop; void InitGraph() { SCCans = dfsclock = 0; memset(high,0,sizeof(high)); memset(ty,0,sizeof(ty)); memset(head,-1,sizeof(head)); Top = 0; STop = 0; } void Link(int u,int v) { edge[Top].next = head[u]; edge[Top].v = v; head[u] = Top++; } void dfs(int s) { high[s] = lowlink[s] = ++dfsclock; S[STop++] = s; int i,v; for(i = head[s] ; i != -1; i = edge[i].next) { v = edge[i].v; if(high[v] == 0) { dfs(v); lowlink[s] = min(lowlink[s],lowlink[v]); } else if(ty[v] == 0) { lowlink[s] = min(lowlink[s],lowlink[v]); } } if(lowlink[s] == high[s]) { SCCans++; do { v = S[--STop]; ty[v] = SCCans; }while(s != v); } } vector<int> vec[MAXP]; int main() { int n,m,u,v,i,j; while(scanf("%d %d",&n,&m) != EOF) { InitGraph(); while(m--) { scanf("%d %d",&u,&v); Link(u,v); } for(i = 1;i <= n; ++i) if(ty[i] == 0) dfs(i); for(i = 1;i <= SCCans; ++i) vec[i].clear(); for(i = 1;i <= n; ++i) { for(j = head[i];j != -1;j = edge[j].next) { if(ty[i] != ty[edge[j].v]) vec[ty[i]].push_back(ty[edge[j].v]); } } } return 0; }
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原文地址:http://blog.csdn.net/zmx354/article/details/45741571