POJ_2553 求出度为0的强连通分支

http://poj.org/problem?id=2553

//强连通分支,求出度为0 的强连通分支#include<iostream>#include<vector>using namespace std;#define M 5001vector<int> graph[M];vector<int> graph_t[M];bool v[M];int outdegree[M], father[M];vector<int> finish;int n, m;void dfs1(int now){v[now] = true;for(int i=0; i<graph[now].size(); i++)if(!v[graph[now][i]])dfs1(graph[now][i]);finish.push_back(now);}void dfs2(int now,int fa){v[now] = true;for(int i=0; i<graph_t[now].size(); i++)if(!v[graph_t[now][i]]){father[graph_t[now][i]] = fa;dfs2(graph_t[now][i],fa);}}int main(){//freopen("in.txt","r",stdin);int i, j, s, t;while(scanf("%d",&n)!=EOF){if(n==0)break;scanf("%d",&m);for(i=1; i<=n; i++){graph[i].clear();graph_t[i].clear();}for(i=1; i<=m; i++){scanf("%d %d",&s, &t);graph[s].push_back(t);graph_t[t].push_back(s);}finish.clear();memset(v,0,sizeof(v));for(i=1; i<=n; i++)if(!v[i])dfs1(i);memset(v,0,sizeof(v));memset(father,0,sizeof(father));memset(outdegree,0,sizeof(outdegree));int cnt = 0;for(i=finish.size()-1; i>=0; i--)if(!v[finish[i]]){cnt++;father[finish[i]] = cnt;dfs2(finish[i],cnt);}/*cout<<cnt<<endl;for(i=1; i<=n; i++)cout<<i<<" "<<father[i]<<endl;*/for(i=1; i<=n; i++)for(j=0; j<graph[i].size(); j++)if(father[i] != father[graph[i][j]])outdegree[father[i] ]++;int tt=0;for(i=1; i<=n; i++)if(outdegree[father[i]] == 0){if(tt != 0)printf(" ");printf("%d",i);tt++;}printf("/n");}return 0;}