HDU 5695 Gym Class

拓扑排序。

#include<cstdio>
#include <iostream>
#include<cstring>
#include<cmath>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;

const int maxn =  + ;
int T, n, m;
bool flag[maxn];

struct Edge
{
    int u, v;
    int nx;
}e[maxn];
int tot;
int head[maxn];
int cnt[maxn];

int L[maxn];
int f;

void init()
{
    tot = ;
    memset(cnt, , sizeof cnt);
    memset(head, -, sizeof head);
    memset(flag, , sizeof flag);
}

void add(int a, int b)
{
    ++tot;
    e[tot].u = a; e[tot].v = b; e[tot].nx = head[a];
    head[a] = tot;
}

void read()
{
    scanf("%d%d", &n, &m);
    for (int i = ; i <= m; i++)
    {
        int u, v; scanf("%d%d", &u, &v);
        add(u, v);
        cnt[v]++;
    }
}

void Sort()
{
    priority_queue<int>Q; f = ;
    for (int i = ; i <= n; i++) if (cnt[i] == ) Q.push(i);
    while (!Q.empty())
    {
        int h = Q.top(); Q.pop();
        L[f++] = h;
        for (int i = head[h]; i != -; i = e[i].nx)
        {
            cnt[e[i].v]--;
            if (cnt[e[i].v] == ) Q.push(e[i].v);
        }
    }

    long long ans = L[];
    long long Min = L[];
    for (int i = ; i < f; i++)
    {
        Min = min(Min,(long long) L[i]);
        ans = ans + Min;
    }

    printf("%lld\n", ans);

}

int main()
{
    scanf("%d", &T);
    while (T--)
    {
        init();
        read();
        Sort();
    }
    return ;
}