2063 过山车

#include <cstdio>
#include <cstring>
//二分匹配经典题
const int maxn=502;
int m, n, used[maxn], boys[maxn], a[maxn][maxn];
int find(int i){
    for(int j=1; j<=n; j++){
        if(a[i][j] && used[j]==0){
            used[j] = 1;
            if(boys[j]==0 || find(boys[j])){
                //注意 这里是find(boys[j]) 而不是 find(j) 
                boys[j] = i;
                return 1;
            }
        }
    }
    return 0;
}
int main(){
    int i, j, k, ans;
    while(scanf("%d", &k) && k){
        memset(a, 0, sizeof(a));
        memset(boys, 0, sizeof(boys));
        scanf("%d %d", &m, &n);
        while(k--){
            scanf("%d %d", &i, &j);
            a[i][j] = 1;
        }
        ans = 0;
        for(i=1; i<=m; i++){
            memset(used, 0, sizeof(used));
            if(find(i)) ans++;
        }
        printf("%d\n", ans);
    }
    return 0;
}