hdu_5695_Gym Class(拓扑排序)

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

题意：中文题，不解释

题解：逆向拓扑字典序就行

#include<cstdio>
#include<string>
#include<set>
#include<vector>
#include<queue>
#include<functional>
using namespace std;
#define MAX 100010
int InDeg[MAX];
int n, m, Count;
int Ans[MAX];
vector<int> v[MAX];
void TopoSort()
{
    priority_queue<int> PQ;
    for(int i=n; i>=1; i--) //找出入度为0的点并放入优先队列
        if(InDeg[i]==0) PQ.push(i);

    while(!PQ.empty()) //BFS
    {
        int Tmp = PQ.top();
        PQ.pop();
        Ans[Count++] = Tmp;
        for(int i=0; i<v[Tmp].size(); i++)
        {
            InDeg[v[Tmp][i]]--;
            if(InDeg[v[Tmp][i]]==0) PQ.push(v[Tmp][i]);
        }
    }
}

int main()
{
    int x, y,t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d%d",&n,&m);
        
        for(int i=0;i<=n;i++)v[i].clear(),InDeg[i]=0;
        Count = 0;
        for(int i=0; i<m; i++)
        {
            scanf("%d%d",&x,&y);
            InDeg[y]++;
            v[x].push_back(y);
        }
        TopoSort();
        int min=1000000000;
        long long an=0;
        for(int i=0; i<Count; i++){
            min=min>Ans[i]?Ans[i]:min;
            an+=min;
        }
        printf("%I64d
",an);
    }
}