拓扑排序

#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#include <queue>
#include <functional>
using namespace std;
#define maxn 100005

int n, a, indegree[maxn];    
vector<int> G[maxn];

void TopoSort()
{
    priority_queue<int, vector<int>, greater<int> >q;
    for (int i = 1; i <= n; i++) 
        if (indegree[i] == 0)q.push(i);
    while (!q.empty()) {
        int u = q.top();
        q.pop();
        printf("v%d ", u);
        for (int i = 0; i < G[u].size(); i++) {
            int v = G[u][i];
            indegree[v]--;
            if (indegree[v] == 0)
                q.push(v);
        }
    }
}

int main()
{
    int u, v;
    cin >> n >> a;
    for (int i = 0; i < a; i++) {
        cin >> u >> v;
        G[u].push_back(v);
        indegree[v]++;
    }
    TopoSort();
    printf("
");
    //system("pause");
    return 0;
}