跑的慢的很。

#include<cstdio>
#define N 4009
#define M 200009

struct node
{
	int v, w, nxt;
}e[M];

int head[N], cnt = 1;

inline void add(int u, int v, int w)
{
	e[++ cnt].v = v, e[cnt].w = w, e[cnt].nxt = head[u], head[u] = cnt;
}

int dis[N], now[N];

#include<queue>

using std::queue;

#include<cstring>

using std::memset;

int s, t;

inline bool bfs()
{
	memset(dis, -1, sizeof dis);
	queue < int > q;
	q.push(s);
	dis[s] = 0;
	register int u, v, i;
	while (!q.empty())
	{
		u = q.front();
		q.pop();
		now[u] = head[u];
		for (i = now[u];i;i = e[i].nxt)
		{
			v = e[i].v;
			if (e[i].w > 0 && dis[v] == -1)
			{
				dis[v] = dis[u] + 1;
				if (v == t)
					return 1;
				q.push(v);
			}
		}
	}
	return 0;
}

inline int min(int a, int b)
{
	return a < b ? a : b;
}

int dfs(register int u, register int flow = 1e9)
{
	if (u == t)
		return flow;
	register int v, w, i, k, lost = flow;
	for (i = now[u];i && lost;i = e[i].nxt)
	{
		v = e[i].v, w = e[i].w;
		now[u] = i;
		if (w > 0 && dis[v] == dis[u] + 1)
		{
			k = dfs(v, min(lost, w));
			if (!k)
			{
				dis[v] = -1;
				continue;
			}
			lost -= k;
			e[i].w -= k;
			e[i ^ 1].w += k;
		}
	}
	return flow - lost;
}

inline int read()
{
	register int ret = 0;
	register bool f = 1;
	register char ch = getchar();
	while (ch < '0' || ch > '9')
		(ch == '-') ? f = 0 : 0, ch = getchar();
	while (ch >= '0' && ch <= '9')
		ret = (ret << 1) + (ret << 3) + (ch ^ 48), ch = getchar();
	return f ? ret : -ret;
}

int main()
{
	register int n, n1 = read(), n2 = read(), m = read(), i, u, v, ans = 0;
	n = n1 + n2;
	s = 0, t = n + 1;
	for (i = 1;i <= m;++ i)
		u = read(), v = read() + n1, add(u, v, 1), add(v, u, 0);
	for (i = 1;i <= n1;++ i)
		add(0, i, 1), add(i, 0, 0);
	for (i = n1 + 1;i <= n1 + n2;++ i)
		add(i, t, 1), add(t, i, 0);
	while (bfs())
		ans += dfs(s);
	printf("%d", ans);
	
	return 0;
}