HDU1285 确定比赛名次【拓扑排序】【优先队列】

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思路：因为要满足字典序的拓扑排序，所以用了STL中的优先队列。

priority_queue<int,vector<int>, greater<int> > Q;

实现了权值小的优先级高，取出的时候保证序号是队列中最小的。

其他的和一般的拓扑排序无区别。

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<queue>
#include<vector>
using namespace std;
const int MAXN = 550;
const int MAXM = 25000;

int head[MAXN],indegree[MAXN],ans[MAXN],N,M;
struct EdgeNode
{
    int to;
    int w;
    int next;
};
EdgeNode Edges[MAXM];

int toposort()
{
    priority_queue<int,vector<int>, greater<int> > Q;
    for(int i = 1; i <= N; i++)
    {
        if(indegree[i]==0)
            Q.push(i);
    }
    int id = 0;
    while(!Q.empty())
    {
        int u;
        ans[id++] = u = Q.top();
        Q.pop();
        for(int k = head[u]; k != -1; k = Edges[k].next)
        {
            indegree[Edges[k].to]--;
            if(!indegree[Edges[k].to])
            {
                Q.push(Edges[k].to);
            }
        }
    }
    if(id == N)
    {
        for(int i = 0; i < id; i++)
        {
            if(i != id-1)
                cout << ans[i] << " ";
            else
                cout << ans[i] << endl;
        }
    }
    else
        return 0;
}
int main()
{
    int x,y;
    while(cin >> N >> M)
    {
        memset(ans,0,sizeof(ans));
        memset(head,-1,sizeof(head));
        memset(Edges,0,sizeof(Edges));
        for(int i = 0; i < M; i++)
        {
            cin >> x >> y;
            Edges[i].to = y;
            Edges[i].w = 1;
            Edges[i].next = head[x];
            head[x] = i;
            indegree[y]++;
        }
        toposort();
    }

    return 0;
}

HDU1285 确定比赛名次【拓扑排序】【优先队列】

原文：http://blog.csdn.net/lianai911/article/details/42088099