最大匹配

匈牙利算法

 

 

AC

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 510, M = 100010;
int h[N], e[M], ne[M], idx;
int n1, n2, m;
bool st[N];
int res;
int match[N];

void add(int a, int b) { // 添加一条边a->b
	e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}

bool find(int u) {

	for (int i = h[u]; ~i; i = ne[i]) {
		int j = e[i];
		if (!st[j]) {
			st[j] = true;
			if (match[j] == 0 || find(match[j])) {
				match[j] = u;

				return true;
			}
		}
	}

	return false;
}
int main() {
	cin >> n1 >> n2 >> m;
	memset(h, -1, sizeof h);
	while (m--) {
		int a, b;
		cin >> a >> b;
		add(a, b);
	}

	for (int i = 1; i <= n1; i++) {

		memset(st, 0, sizeof st);

		if (find(i))res++;
	}

	cout << res;
	return 0;
}