【luogu P1402 酒店之王】 题解

题目链接：https://www.luogu.org/problemnew/show/P1402

菜

#include <queue>

#include <cstdio>

#include <cstring>

#include <iostream>

#include <algorithm>

using namespace std;

const int maxn = 1e6 + 10;

const int inf = 1e9;

int n, p, q, s, t, deep[maxn], maxflow;

struct edge{

	int flow, next, to;

}e[maxn<<2];

int head[maxn], cnt = -1;

queue<int> q1;

void add(int u, int v, int w)

{

	e[++cnt].flow = w; e[cnt].next = head[u]; e[cnt].to = v; head[u] = cnt;

	e[++cnt].flow = 0; e[cnt].next = head[v]; e[cnt].to = u; head[v] = cnt;

}

bool bfs(int s, int t)

{

	memset(deep, 0x7f, sizeof(deep));

	while(!q1.empty()) q1.pop();

	q1.push(s); deep[s] = 0;

	while(!q1.empty())

	{

		int now = q1.front(); q1.pop();

		for(int i = head[now]; i != -1; i = e[i].next)

		{

			if(deep[e[i].to] > inf && e[i].flow)

			{

				deep[e[i].to] = deep[now] + 1;

				q1.push(e[i].to);

			}

		}

	}

	if(deep[t] < inf) return true;

	else return false;

}

int dfs(int now, int t, int limit)

{

	if(!limit || now == t) return limit;

	int flow = 0, f;

	for(int i = head[now]; i != -1; i = e[i].next)

	{

		if(deep[e[i].to] == deep[now] + 1 && (f = dfs(e[i].to, t, min(e[i].flow, limit))))

		{

			flow += f;

			limit -= f;

			e[i].flow -= f;

			e[i^1].flow += f;

			if(!limit) break;

		}

	}

	return flow;

}

void Dinic(int s, int t)

{

	while(bfs(s, t))

	maxflow += dfs(s, t, inf);

}

int main()

{

	memset(head, -1, sizeof(head));

	scanf("%d%d%d",&n,&p,&q);

	s = 1, t = n + n + p + q + 2;

	for(int i = 1; i <= n; i++)

		for(int j = 1; j <= p; j++)

		{

			int u;

			scanf("%d",&u);

			if(u == 1)

			{

				add(j + n + n + 1, i + 1, 1);

			}

		}

	for(int i = 1; i <= n; i++)

		for(int j = 1; j <= q; j++)

		{

			int u;

			scanf("%d",&u);

			if(u == 1)

			{

				add(i + n + 1, j + n + n + p + 1, 1);

			}

		}

	for(int i = 1; i <= n; i++)

	add(i + 1, i + n + 1, 1);

	for(int i = 1; i <= p; i++)

	add(s, i + n + n + 1, 1);

	for(int i = 1; i <= q; i++)

	add(i + n + n + p + 1, t, 1);

	Dinic(s, t);

	printf("%d",maxflow);

	return 0;

}