Dinic递归版

struct Edge
{
	int from, to, cap, flow;
	Edge(){}
	Edge(int from, int to, int cap, int flow) : from(from), to(to), cap(cap), flow(flow){}
};
int n, m, s, t;
vector <Edge> edges;
vector <int> G[maxn];
bool vis[maxn];
int d[maxn];
int cur[maxn];

void AddEdge(int from, int to, int cap)
{
	edges.push_back(Edge(from, to, cap, 0));
	edges.push_back(Edge(to, from, 0, 0));
	m = edges.size();
	G[from].push_back(m-2);
	G[to].push_back(m-1); 
}
bool BFS()
{
	memset(vis, 0, sizeof(vis));
	queue <int> Q;
	Q.push(s);
	d[s] = 0;
	vis[s] = 1;
	while(!Q.empty())
	{
		int x = Q.front(); Q.pop();
		for(int i = 0; i < G[x].size(); i++)
		{
			Edge& e = edges[G[x][i]];
			if(!vis[e.to] && e.cap > e.flow)
			{
				vis[e.to] = 1;
				d[e.to] = d[x] + 1;
				Q.push(e.to);
			}
		}
	}
	return vis[t];
}
int DFS(int x, int a)
{
	if(x == t || a == 0)
		return a;
	int flow = 0, f;
	for(int& i = cur[x]; i < G[x].size(); i++)
	{
		Edge& e = edges[G[x][i]];
		if(d[x] + 1 == d[e.to] && (f = DFS(e.to, min(a, e.cap-e.flow))) > 0)
		{
			e.flow += f;
			edges[G[x][i]^1].flow -= f;
			flow += f;
			a -= f;
			if(a == 0)
				break;
		}
	}
	return flow;
}

int Maxflow()
{
	int flow = 0;
	while(BFS())
	{
		memset(cur, 0, sizeof(cur));
		flow += DFS(s, INF);
	}
	return flow;
}