奖金——Topsort

题目

代码

#include <bits/stdc++.h>
using namespace std;
const int N = 1e4+10, M = 2e4+10;
int h[N], e[M], ne[M], idx;
int d[N], in[N], cnt;
int n, m;
queue<int> q;
void add(int a, int b)  // 添加一条边a->b
{
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}

bool bfs()
{
    for(int i = 1; i <= n; i++)
        if(!in[i]) q.push(i), d[i] = 0;
    
    while(q.size())
    {
        int u = q.front(); q.pop(); cnt++;
        
        for(int i = h[u]; ~i; i = ne[i])
        {
            int j = e[i];
            if(--in[j] == 0)
            {
                if(~d[j])
                {
                    if(d[j] != d[u] + 1) return false;
                    
                }
                else d[j] = d[u] + 1;
                q.push(j);
            }
        }
    }
    
    return cnt == n;
}
int main()
{
    cin >> n >> m;
    memset(h, -1, sizeof h);
    for(int i = 1; i <= m; i++)
    {
        int a, b;
        cin >> a >> b;
        add(b, a);
        in[a]++;
    }
    
    memset(d, -1, sizeof d);
    bool success = bfs();
    if(!success)
    {
        cout << "Poor Xed";
        return 0;
    }
    
    int ans = 0;
    for(int i = 1; i <= n; i++)
        ans += 100 + d[i];
        
    cout << ans;
}