hdu_1269, 强连通分量的学习

http://acm.hdu.edu.cn/showproblem.php?pid=1269

#include<cstdio>
#include<cstring>

const int maxn = 10000 + 10;
struct Edge{
    int to, next;
}e[maxn*10];
int head[maxn], index;
int dfn[maxn], low[maxn];
int belong[maxn], vis[maxn];
int step, color;

void add_edge(int u, int v){
    e[index].to = v, e[index].next = head[u];
    head[u] = index ++;
}
void init_edge(){
    memset(head, -1, sizeof head);
    index= 0;
}
int n, m;
int stack[maxn], top;
void targan(int u){
    dfn[u] = low[u] = ++step;
    stack[top++] = u;
    vis[u] = 1;
    for(int i = head[u]; i != -1; i = e[i].next){
        int v = e[i].to;
        if(!dfn[v]){
            targan(v);
            if(low[u] > low[v])
              low[u] = low[v];
        }else
          if(vis[v] && low[u] > dfn[v])
            low[u] = dfn[v];
    }
    if(dfn[u] == low[u]){
        color ++;
        int s;
        do{
            s = stack[top--];
            vis[s] = 0;
            belong[s] = color;
        }while(s != u);
    }
}
void solve(){
    memset(vis, 0, sizeof vis);
    memset(dfn, 0, sizeof dfn);
    step = color = top = 0;
    for(int i = 1; i <= n; i ++)
      if(!dfn[i])
        targan(i);
}
int main(){
    while(scanf("%d%d", &n, &m), n||m){
        init_edge();
        for(int i = 0; i < m; i ++){
            int u, v;
            scanf("%d%d", &u, &v);
            add_edge(u, v);
        }
        solve();
        if(color == 1)
          puts("Yes");
        else
          puts("No");
    }
    return 0;
}

这个也当作模板吧