比武定工资（拓扑排序）

 

#include<bits/stdc++.h>
#define MAX 6010
using namespace std;
queue<pair<int, int> >q;
vector<int> g[MAX];
pair<int, int> ls;
int cnt[MAX], n, m, x, y, ans = 0, sum = 0;
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> n >> m;
	for(int i = 0; i < m; i++){
		cin >> x >> y;
		g[y].push_back(x);
		cnt[x]++;
	}
	for(int i = 1; i <= n; i++)
		if(!cnt[i]) q.push(make_pair(i, 100));
	while(q.size()){
		ls = q.front();
		q.pop();
		ans += ls.second, sum ++;
		for(int i = 0; i < g[ls.first].size(); i++){
			cnt[g[ls.first][i]]--;
			if(!cnt[g[ls.first][i]]) q.push(make_pair(g[ls.first][i], ls.second + 1));
		}	
	}
	if(sum == n) cout << ans;
	else cout << "no solution";
	return 0;
}