【bzoj4554】[Tjoi2016&Heoi2016]游戏 二分图最大匹配

#include <cstdio>
#include <cstring>
#include <queue>
#define N 6000
#define M 300000
using namespace std;
queue<int> q;
int map[60][60] , bx[60][60] , by[60][60] , tx , ty , head[N] , to[M] , val[M] , next[M] , cnt = 1 , s , t , dis[N];
char str[60];
void add(int x , int y , int z)
{
	to[++cnt] = y , val[cnt] = z , next[cnt] = head[x] , head[x] = cnt;
	to[++cnt] = x , val[cnt] = 0 , next[cnt] = head[y] , head[y] = cnt;
}
bool bfs()
{
	int x , i;
	memset(dis , 0 , sizeof(dis));
	while(!q.empty()) q.pop();
	dis[s] = 1 , q.push(s);
	while(!q.empty())
	{
		x = q.front() , q.pop();
		for(i = head[x] ; i ; i = next[i])
		{
			if(val[i] && !dis[to[i]])
			{
				dis[to[i]] = dis[x] + 1;
				if(to[i] == t) return 1;
				q.push(to[i]);
			}
		}
	}
	return 0;
}
int dinic(int x , int low)
{
	if(x == t) return low;
	int temp = low , i , k;
	for(i = head[x] ; i ; i = next[i])
	{
		if(val[i] && dis[to[i]] == dis[x] + 1)
		{
			k = dinic(to[i] , min(temp , val[i]));
			if(!k) dis[to[i]] = 0;
			val[i] -= k , val[i ^ 1] += k;
			if(!(temp -= k)) break;
		}
	}
	return low - temp;
}
int main()
{
	int n , m , i , j , ans = 0;
	scanf("%d%d" , &n , &m);
	for(i = 1 ; i <= n ; i ++ )
	{
		scanf("%s" , str + 1);
		for(j = 1 ; j <= m ; j ++ )
			map[i][j] = (str[j] == ‘*‘ ? 0 : str[j] == ‘x‘ ? 1 : 2);
	}
	for(i = 1 ; i <= n ; i ++ )
	{
		tx ++ ;
		for(j = 1 ; j <= m ; j ++ )
		{
			bx[i][j] = tx;
			if(map[i][j] == 2) tx ++ ;
		}
	}
	for(j = 1 ; j <= m ; j ++ )
	{
		ty ++ ;
		for(i = 1 ; i <= n ; i ++ )
		{
			by[i][j] = ty;
			if(map[i][j] == 2) ty ++ ;
		}
	}
	s = 0 , t = tx + ty + 1;
	for(i = 1 ; i <= tx ; i ++ ) add(s , i , 1);
	for(i = 1 ; i <= ty ; i ++ ) add(i + tx , t , 1);
	for(i = 1 ; i <= n ; i ++ )
		for(j = 1 ; j <= m ; j ++ )
			if(!map[i][j])
				add(bx[i][j] , by[i][j] + tx , 1);
	while(bfs()) ans += dinic(s , 1 << 30);
	printf("%d\n" , ans);
	return 0;
}