HDU 5961 传递 BFS

**题意：**中文题，就是判断一个竞赛图拆成两个图，判断是否都传递
**思路：**分别BFS判深度即可，用这种方法注意要进行读入优化。

/** @Date    : 2016-11-18-20.00

  * @Author  : Lweleth (SoungEarlf@gmail.com)

  * @Link    : https://github.com/

  * @Version :

  */

#include <stdio.h>

#include <iostream>

#include <string.h>

#include <algorithm>

#include <utility>

#include <vector>

#include <map>

#include <set>

#include <string>

#include <stack>

#include <queue>

//#include<bits/stdc++.h>

#define LL long long

#define pii pair<int ,int>

#define mp(x,y) make_pair((x), (y))

#define fi first

#define se second

#define MMF(x) memset((x),0,sizeof(x))

#define MMI(x) memset((x), INF, sizeof(x))

using namespace std;



const int INF = 0x3f3f3f3f;

const int N = 1e5+2000;







vector<int >ed1[2100], ed2[2100];

int vis[2100];



int main()

{

    int T;

    scanf("%d", &T);

    while(T--)

    {

        int n;

        scanf("%d", &n);



        for(int i = 1; i <= n; i++)

            ed1[i].clear(), ed2[i].clear();



        getchar();

        for(int i = 1; i <= n; i++)

        {

            for(int j = 1; j <= n; j++)

            {

                char t;

                t = getchar();//读入优化

                if(t == 'P')

                    ed1[i].push_back(j);

                else if(t =='Q')

                    ed2[i].push_back(j);

            }

            getchar();

        }



        int flag = 0;

        for(int i = 1; i <= n; i++)

        {

            queue<int>q;

            q.push(i);

            MMF(vis);

            while(!q.empty())

            {

                int nw = q.front();

                q.pop();

                for(int j = 0; j < ed1[nw].size(); j++)

                {

                    int nl = ed1[nw][j];

                    if(vis[nl] == 0)//第二层的新点，表明第一层不能到达 直接退出

                    {

                        vis[nl] = vis[nw] + 1;

                        if(nw != i || vis[nl] >= 2)

                        {

                            flag = 1;

                            break;

                        }

                        q.push(nl);

                    }

                }

                if(flag)

                    break;

            }

            while(!q.empty())

                q.pop();

            MMF(vis);

            q.push(i);

            while(!q.empty())

            {

                int nw = q.front();

                q.pop();

                for(int j = 0; j < ed2[nw].size(); j++)

                {

                    int nl = ed2[nw][j];

                    if(vis[nl] == 0)

                    {

                        vis[nl] = vis[nw] + 1;

                        if(nw != i || vis[nl] >= 2)

                        {

                            flag = 1;

                            break;

                        }

                        q.push(nl);

                    }

                }

                if(flag)

                    break;

            }

        }

        if(flag)

            puts("N");

        else puts("T");



    }

    return 0;

}