HDU 1281 棋盘游戏

题解：将所有的横坐标看作一边的点，纵坐标看作另一边的点，然后二分图匹配即可，建图很巧妙……

#include <cstdio> 

#include <cstring> 

#define maxn 105  

bool map[maxn][maxn],vis[maxn];  

int n,m,k,mark[maxn],edge[maxn*maxn][2];  

bool dfs(int v){  

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

        if(vis[i]||!map[i][v])  

            continue;  

        vis[i]=true;  

        if(mark[i]==0||dfs(mark[i])){  

            mark[i]=v;  

            return true;  

        }  

    }  

    return false;  

}    

int Hungarian(){

    int count=0;  

    memset(mark,0,sizeof(mark));  

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

        memset(vis,false,sizeof(vis));  

        if(dfs(i)) count++;  

    }  

    return count;  

}  

int main(){  

    int i,sum,num=1;  

    while(scanf("%d%d%d",&n,&m,&k)!=EOF){  

        memset(map,false,sizeof(map));  

        for(i=0;i<k;i++){  

            scanf("%d%d",&edge[i][0],&edge[i][1]);  

            map[edge[i][0]][edge[i][1]] = true;  

        }  

        int max=Hungarian();   

        for(i=sum=0;i<k;i++){  

            map[edge[i][0]][edge[i][1]]=false;  

            if(max>Hungarian()) sum++;  

            map[edge[i][0]][edge[i][1]]=true;  

        }  

        printf("Board %d have %d important blanks for %d chessmen.\n",num++,sum,max);  

    }  

    return 0;  

}