拓撲排序

模板：

#include<bits/stdc++.h>
#define rint register int
#define deb(x) cerr<<#x<<" = "<<(x)<<'\n';
using namespace std;
typedef long long ll;
typedef pair <int,int> pii;
const ll mod = 1e9 + 7;
const int maxn = 3e5 + 10;
int n, m, cnt;
int in[maxn], tp[maxn];
vector <int> v[maxn];

void tp_sort(){
	queue <int> Q;
	for(int i=1; i<=n; i++)
		if(!in[i]) Q.push(i);
	while(!Q.empty()){
		int q = Q.front();
		Q.pop();
		tp[cnt++] = q;
		for(auto i : v[q]){
			in[i]--;
			if(!in[i]) Q.push(i);
		}
	}
}

int main() {
	scanf("%d%d", &n, &m);
	for(int i=0, x, y; i<m; i++){
		scanf("%d%d", &x, &y);
		v[x].push_back(y);
		in[y]++;
	}
	
	tp_sort();
	for(int i=0; i<cnt; i++) 
		printf("%d ", tp[i]);
}