二分图的最大匹配

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
const int N = 510, M = 100010;
int n1, n2, m;
int h[N], e[M], ne[M], idx;
int match[N];
bool st[N];
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] || 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++)
    {
        memset(st, false, sizeof st);
        if(find(i)) res++;
    }
    cout<<res<<endl;
}