poj 1422 Air Raid 最小路径覆盖

对于路径覆盖概念请点击以下链接：

　　Path Cover

 

#include<stdio.h>

#include<stdlib.h>

#include<string.h>



const int N = 150;

int n, m;



int ma[N],mb[N];

bool g[N][N], vis[N];



int path( int u ){

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

        if( g[u][v] && !vis[v] ){

            vis[v] = 1;

            if( ma[v] == -1 || path( ma[v] )){

                ma[v] = u; mb[u] = v;

                return 1;    

            }    

        }    

    }    

    return 0;

}

int main(){

    int T;

    scanf("%d",&T);

    while(T--){

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

        memset( g, 0, sizeof(g));

        int a, b;

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

            scanf("%d%d", &a,&b);

            g[a][b] = 1;

        }

        memset( ma, 0xff, sizeof(ma));

        memset( mb, 0xff, sizeof(mb));

        int ans = 0;

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

            if( mb[i] == -1 ){

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

                ans += path( i );    

            }    

        } 

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

    }

    return 0;    

}