拓扑排序

拓扑排序

#include<bits/stdc++.h>
using namespace std;
vector<int> g[1001];
priority_queue<int,vector<int>,greater<int> > q;
int rudu[1001];
vector<int> ans;
int main()
{
	int n,m;
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		int x,y;
		cin>>x>>y;
		g[x].push_back(y);
		rudu[y]++;
	}
	for(int i=1;i<=n;i++){
		if(rudu[i]==0){
			q.push(i);
		}
	}
	while(!q.empty()){
		int f=q.top();
		q.pop();
		ans.push_back(f);
		for(int i=0;i<g[f].size();i++){
			int to=g[f][i];
			rudu[to]--;
			if(rudu[to]==0){
				q.push(to);
			}
		}
	}
	if(ans.size()!=n){
		cout<<-1<<endl;
		return 0;
	}
	for(int i=0;i<n;i++){
		cout<<ans[i]<<" ";
	}
	return 0;
}