二分圖匹配(簡單題)POJ 1274 The Perfect Stall

The Perfect Stall

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 8898		Accepted: 4136

Description

Farmer John completed his new barn just last week, complete with all the latest milking technology. Unfortunately, due to engineering problems, all the stalls in the new barn are different. For the first week, Farmer John randomly assigned cows to stalls, but it quickly became clear that any given cow was only willing to produce milk in certain stalls. For the last week, Farmer John has been collecting data on which cows are willing to produce milk in which stalls. A stall may be only assigned to one cow, and, of course, a cow may be only assigned to one stall.
Given the preferences of the cows, compute the maximum number of milk-producing assignments of cows to stalls that is possible.

Input

The input includes several cases. For each case, the first line contains two integers, N (0 <= N <= 200) and M (0 <= M <= 200). N is the number of cows that Farmer John has and M is the number of stalls in the new barn. Each of the following N lines corresponds to a single cow. The first integer (Si) on the line is the number of stalls that the cow is willing to produce milk in (0 <= Si <= M). The subsequent Si integers on that line are the stalls in which that cow is willing to produce milk. The stall numbers will be integers in the range (1..M), and no stall will be listed twice for a given cow.

Output

For each case, output a single line with a single integer, the maximum number of milk-producing stall assignments that can be made.

Sample Input

5 52 2 53 2 3 42 1 53 1 2 51 2 

Sample Output

4

/*題目大意：n頭牛到m個畜欄,每頭牛隻有在自己喜歡的畜欄產奶，求最大產奶量;題目求解：很明顯匈牙利演算法求二分圖最大匹配.PS：剛開始沒看懂輸入輸出，糾結了半天(還以為會有不同畜欄的產奶量，要用最大流做)，寫代碼花了2-3分就寫完了，1Y，這題真的是基礎的一塌糊塗.Source CodeProblem: 1274   User: wawadimu Memory: 348K   Time: 16MS Language: C++   Result: Accepted Source Code */#include<iostream>using namespace std;#define maxn 210int map[maxn][maxn];int match[maxn];bool vis[maxn];int n,m;//n(num_cow),m(num_stall)bool dfs(int u){for(int v=1;v<=n;v++){if(!vis[v] && map[u][v]){vis[v]=true;if(match[v]==0 || dfs(match[v])) {match[v]=u;return true;}}}return false;}int main(){//freopen("1274.txt","r",stdin);int i,k,j;int cnt;while(scanf("%d%d",&n,&m)!=EOF){memset(map,0,sizeof(map));memset(match,0,sizeof(match));for(i=1;i<=n;i++){scanf("%d",&cnt);while(cnt--){scanf("%d",&k);map[i][k]=1;}}int ans=0;for(i=1;i<=n;i++){memset(vis,0,sizeof(vis));if(dfs(i)) ans++;}printf("%d/n",ans);}return 1;}