HDU 3081 Marriage Match II 二分+最大流

题目来源：HDU 3081 Marriage Match II

题意：

思路：

错误代码 纠结不知道哪错了 先放一放

#include <cstdio>
#include <queue>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 1010;
const int INF = 999999999;
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 a[maxn];
int b[maxn];
int c[maxn][maxn];
int f[maxn];
int n, m, s, t, k1, k2;
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;
}

int find(int x)
{
	if(x != f[x])
		return f[x] = find(f[x]);
	return f[x];
}

void build(int mid)
{
	edges.clear();
    for(int i = 0; i <= 2*n+1; i++)
		G[i].clear();
	s = 0;
	t = 2*n+1;
	for(int i = 1; i <= n; i++)
	{
		AddEdge(s, i, mid);
		AddEdge(i+n, t, mid);
	}

	memset(c, 0, sizeof(c));
	for(int i = 0; i < k1; i++)
	{
		for(int j = 1; j <= n; j++)
		{
			int u = a[i];
			int v = b[i];
			if(f[u] == f[j] && !c[j][v])
			{
				AddEdge(j, v+n, 1);
				c[j][v] = 1;
			}
		}
	}
}
int main()
{
    int T;
    scanf("%d", &T);
    while(T--)
    {
        scanf("%d %d %d", &n, &k1, &k2);
        for(int i = 0; i <= 2*n+1; i++)
        {
			f[i] = i;
        }
        for(int i = 0; i < k1; i++)
        {
            scanf("%d %d", &a[i], &b[i]);
            //b[i] += n;
        }
        for(int i = 0; i < k2; i++)
        {
        	int u, v;
        	scanf("%d %d", &u, &v);
        	int x = find(u);
        	int y = find(v);
        	if(x != y)
        		f[x] = y;
        }
		for(int i = 1; i <= n; i++)
			f[i] = find(i);
        int l = 0, r = n;
        int ans = 0;
        while(l <= r)
        {
        	int mid = (l + r) >> 1;
        	build(mid);
        	if(Maxflow() == mid*n)
        	{
        		ans = mid;
        		l = mid + 1;
        	}
        	else
        		r = mid - 1;
        }
       	printf("%d\n", ans);
    }
    return 0;
}

HDU 3081 Marriage Match II 二分+最大流