拓扑排序（DFS实现）

~~~c++

#include<bits/stdc++.h>
using namespace std;

int n,m;
int graph[110][110];
int vis[110];
int ans[110],t;

bool dfs(int u){
    vis[u] = -1;
    for(int i = 1; i <= n; i++){
        if(graph[u][i]){
            if(vis[i] < 0) return false;
            if(vis[i] == 0 && !dfs(i)){
                return false;
            }
        }
    }
    vis[u] = 1;
    ans[t++] = u;
    return true;
}
int main() {
    while(cin>>n>>m){
        if(n == 0 && m == 0) break;
        memset(graph,0,sizeof(graph));
        memset(vis,0,sizeof(vis));
        t = 0;
        int u,v;
        for(int i = 0; i < m; i++){
            cin>>u>>v;
            graph[u][v] = 1;
        }
        bool flag = true;
        for(int i = 1; i <= n; i++){
            if(vis[i] == 0){
                if(!dfs(i)){
                    flag = false;
                    break;
                }
            }
        }
        for(int i = n -1; i >=0; i--){
            if(i != n - 1) cout<<" ";
            cout<<ans[i];
        }
        cout<<endl;
    }
    return 0;
}

~~~

> uva10305