HDU 5695 Gym Class 拓扑排序

题目链接：

http://acm.hdu.edu.cn/showproblem.php?pid=5695

题解：

求出字典序最大的拓扑序。然后把求好的数列翻转过来就是满足条件的数列，然后模拟求一下value就可以了。

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

const int maxn = 1e5 + 10;
typedef long long LL;

struct Edge {
    int v, ne;
    Edge(int v, int ne) :v(v), ne(ne) {}
    Edge() {}
}egs[maxn*2];

int n, m;
int head[maxn], ind[maxn],tot;

void addEdge(int u, int v) {
    egs[tot] = Edge(v, head[u]);
    head[u] = tot++;
}

void init() {
    tot = 0;
    memset(ind, 0, sizeof(ind));
    memset(head, -1, sizeof(head));
}

int main() {
    int tc;
    scanf("%d", &tc);
    while (tc--) {
        init();
        scanf("%d%d", &n, &m);
        for (int i = 0; i < m; i++) {
            int u, v;
            scanf("%d%d", &u, &v);
            addEdge(u, v);
            ind[v]++;
        }
        priority_queue<int> pq;
        for (int i = 1; i <= n; i++) {
            if (ind[i] == 0) pq.push(i);
        }
        vector<int> ans;
        while (!pq.empty()) {
            int u = pq.top(); pq.pop();
            ans.push_back(u);
            int p = head[u];
            while (p != -1) {
                Edge& e = egs[p];
                ind[e.v]--;
                if (ind[e.v] == 0) {
                    pq.push(e.v);
                }
                p = e.ne;
            }
        }
        LL sum = ans[0]; int mi = ans[0];
        for (int i = 1; i < ans.size(); i++) {
            mi = min(mi, ans[i]);
            sum += mi;
        }
        printf("%lld
", sum);
    }
    return 0;
}