2015-2016 ACM-ICPC, NEERC, Moscow Subregional Contest（K. King's Rout）（拓扑排序）

King's Rout

题目链接：

http://codeforces.com/gym/100792/problem/K

解题思路：

将顺序反过来，然后再求拓扑排序。注意：最后将结果倒着输出。

AC代码：

#include <bits/stdc++.h>
using namespace std;

const int N = 200005;
int n,m;
int indegree[N];
priority_queue<int> q;
vector<int> v[N];
vector<int> ans;

void solve(int cur){
    int len = v[cur].size();
    for(int i = 0; i < len; ++i){
        int tmp = v[cur][i];
        --indegree[tmp];
        if(!indegree[tmp])
            q.push(tmp);
    }
}

int main(){
    while(~scanf("%d%d",&n,&m)){
        for(int i = 0; i <= n; ++i)
            v[i].clear();
        ans.clear();
        while(!q.empty())
            q.pop();
        memset(indegree,0,sizeof(indegree));
        int a,b;
        for(int i = 0; i < m; ++i){
            scanf("%d%d",&a,&b);
            ++indegree[a];
            v[b].push_back(a);
        }
        for(int i = 1; i <= n; ++i)
            if(indegree[i] == 0)
                q.push(i);
        while(!q.empty()){
            int cur = q.top();
            ans.push_back(cur);
            q.pop();
            solve(cur);
        }
        for(int i = n-1; i > 0; --i)
            printf("%d ",ans[i]);// 最后倒着输出。
        printf("%d\n",ans[0]);
    }
    return 0;
}