CF-825E Minimal Labels （反向拓扑）

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 10;
int n, m;
vector<int> graph[MAXN];
priority_queue<int, vector<int>, less<int> > Q;
int a[MAXN], indegree[MAXN];
int main() {
    scanf("%d%d", &n, &m);
    for(int i = 0; i < m; i++) {
        int x, y;
        scanf("%d%d", &x, &y);
        indegree[x]++;//把出度看出入度 
        graph[y].push_back(x);//反向建立图 
    }
    for(int i = 1; i <= n; i++) 
        if(indegree[i] == 0) Q.push(i);
    int t = n;
    while(!Q.empty()) {
        int u  = Q.top(); Q.pop();
        a[u] = t--;//越大的值标号越大
        for(int i = 0; i <  graph[u].size(); i++) {
            if(--indegree[ graph[u][i]] == 0) Q.push( graph[u][i]);
        }
    }
    for(int i = 1; i <= n; i++) {
        printf("%d ", a[i]);
    }
    return 0;
}