拓扑排序模板

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

const int maxn = 1e4 + 5;
vector<int> G[maxn];
int in[maxn],seq[maxn];
int n,m,cnt = 0;

void topology(){
    for(int i = 1;i <= n;i++){
        if(in[i] == 0) seq[++cnt] = i;
    }
    int head = 1;
    while(head <= cnt){
        int u = seq[head];
        int ans = cnt;
        for(int i = 0;i < G[u].size();i++){
            int v = G[u][i];
            in[v]--;
            if(in[v] == 0) seq[++cnt] = v;
        }
        head++;
    }
    //当cnt不等于n时，说明这图有环
}

int main(){ 
    scanf("%d %d",&n,&m);
    for(int i = 1;i <= m;i++){
        int x,y;
        scanf("%d %d",&x,&y);
        G[x].push_back(y);
        in[y]++;;
    }
    topology();
    for(int i = 1;i <= cnt;i++) printf("%d\n",seq[i]);
}