--hdu 1151 - > 双向路径搜索解决覆盖问题

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;

int ms[125][125];
int vis[125];
int n,m;

bool dfs(int u){

    bool wala = false;

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

        if(vis[i] == 0 &&ms[u][i]){

            vis[i] = 1;
            dfs(i);
            wala = true;
            break;

        }else if(ms[u][i] && dfs(i)){

            wala = true;
            break;

        }


    }
    return wala;
}

bool re_dfs(int u){

    bool wala = false;

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

        if(vis[i] == 0&&ms[i][u]){

            vis[i] = 1;
            re_dfs(i);
            wala = true;
            break;

        }else if(ms[i][u] &&re_dfs(i)){

            wala = true;
            break;

        }


    }
    return wala;
}

int main(){

     int t ;



     scanf("%d",&t);

     while(t--){

        int ans = 0;

        memset(ms,0,sizeof(ms));
        memset(vis,0,sizeof(vis));



        scanf("%d%d",&n,&m);

        int u,v;

        for(int i = 0;i<m;i++){

            scanf("%d%d",&u,&v);

            ms[u][v] = 1;

        }

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

            if(!vis[i]){

                vis[i] = 1;
                dfs(i);
                re_dfs(i);
                ans ++;

            }


        }

        printf("%d\n",ans);

     }

}