hdu 1281 棋盘游戏

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题目地址：http://acm.hdu.edu.cn/showproblem.php?pid=1281

本题为简单最小点覆盖。只需先求出最小点覆盖然后枚举所有的点。

#include<stdio.h>#include<string.h>#define maxn 105bool 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(){//匈牙利算法求二分图的最大匹配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 ;//求最小点覆盖max = Hungarian();//枚举所有的点。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;}