[POJ2226]Muddy Fields（二分图匹配）

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <list>
#include <map>
#include <iostream>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <iomanip>
#define LL long long
#define inf 0x3f3f3f3f
#define INF 0x3f3f3f3f3f3f
#define PI 3.1415926535898
#define F first
#define S second
#define lson  rt << 1
#define rson  rt << 1 | 1
using namespace std;

const int maxn = 57;
const int maxm = 2e5 + 7;
int n, m;
char mp[maxn][maxn];
int r[maxn][maxn], c[maxn][maxn];
int cnt = 0, rnum;

vector <int> G[6000];
int vis[2 * maxn * maxn], link[2 * maxn * maxn];
bool dfs(int u)
{
    for (int i = 0; i < G[u].size(); i++)
    {
        int v = G[u][i];
        if (!vis[v])
        {
            vis[v] = 1;
            if (!link[v] || dfs(link[v]))
            {
                link[v] = u;
                return true;
            }
        }
    }
    return false;
}
int max_match()
{
    memset(link, 0, sizeof(link));
    int ans = 0;
    for (int i = 1; i <= rnum; i++)
    {
        memset(vis, 0, sizeof(vis));
        if (dfs(i)) ans++;
    }
    return ans;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            cin >> mp[i][j];
            if (mp[i][j] == ‘*‘)
            {
                if (mp[i - 1][j] == ‘*‘) r[i][j] = r[i - 1][j];
                else r[i][j] = ++cnt;
            }
        }
    }
    rnum = cnt;

    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            if (mp[i][j] == ‘*‘)
            {
                if (mp[i][j - 1] == ‘*‘) c[i][j] = c[i][j - 1];
                else c[i][j] = ++cnt;
                G[r[i][j]].push_back(c[i][j]);
           }
        }
    }
    cout << max_match() << endl;

}