17.二分图的最大匹配

 

#include <bits/stdc++.h>
using namespace std;
const int N = 510, M = 100010;
int h[N], e[M], ne[M], idx;
int n1, n2, m;
bool st[N]; //判重
int match[N]; //右边点对应的点
void add(int a, int b) {
    e[idx] = b;
    ne[idx] = h[a];
    h[a] = idx++;
}
bool find(int x) {
    for (int i = h[x]; i != -1; i = ne[i]) {
        int j = e[i];
        if (!st[j]) {
            st[j] = true;
            if (match[j] == 0 || find(match[j])) {
                match[j] = x;
                return true;
            }
        }
    }
    return false;
}
int main() {
    memset(h, -1, sizeof h);
    cin >> n1 >> n2 >> m;
    while (m--) {
        int a, b;
        cin >> a >> b;
        add(a, b);
    }
    int res = 0;
    for (int i = 1; i <= n1; i++) { //看每个男生
        memset(st, false, sizeof st); //清空每个妹子
        if (find(i)) {
            res++;
        }
    }
    cout << res << endl;
    return 0;
}