[面试备] 暴搜 or 二分图的经典升级 ： hdu 1045 Fire Net 示例 [ 二分图 ]

二分图匹配 建图的经典之作

#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <vector>
#include <stack>
#include <deque>
#include <queue>
#include <bitset>
#include <list>
#include <map>
#include <set>
#include <iterator>
#include <algorithm>
#include <functional>
#include <utility>
#include <sstream>
#include <climits>
#include <cassert>
#define BUG puts("here!!!");

using namespace std;
const int N = 5;
const int M = 30;
char str[N][N];
int p[N][N];
int rp[N][N];
int mmap[M][M];
int pre[M];
bool vis[M];
int n;
int x_id, y_id;
bool dfs(int u) {
	for(int i = 1; i <= y_id; i++) {
		if(mmap[u][i] && !vis[i]) {
			vis[i] = true;
			if(pre[i] == 0 || dfs(pre[i])) {
				pre[i] = u;
				return true;
			}
		}
	}
	return false;
}
int maxMatch() {
	memset(pre, 0, sizeof(pre));
	int num = 0;
	for(int i = 1; i <= x_id; i++) {
		memset(vis, 0, sizeof(vis));
		if(dfs(i)) num++;
	}
	return num;
}
int main() {
	while(cin >> n, n) {
		for(int i = 0; i < n; i++) {
			scanf("%s", str[i]);
		}
		memset(p, 0, sizeof(p));
		memset(rp, 0, sizeof(rp));
		x_id = 0, y_id = 0;
		for(int i = 0; i < n; i++) {
			int k = 0;
			while(k < n) {
				if(str[i][k] == '.') {
					++x_id;
					while(k < n && str[i][k] != 'X') {
						p[i][k] = x_id;
						k++;
					}
				}
				else k++;
			}
		}
		for(int i = 0; i < n; i++) {
			int k = 0;
			while(k < n) {
				if(str[k][i] == '.') {
					++y_id;
					while(k < n && str[k][i] != 'X') {
						rp[k][i] = y_id;
						k++;
					}
				}
				else k++;
			}
		}
		memset(mmap, 0, sizeof(mmap));
		for(int i = 0; i < n; i++) {
			for(int j = 0; j < n; j++) {
				if(str[i][j] == '.') {
					mmap[p[i][j]][rp[i][j]] = 1;
				}
			}
		}
		printf("%d\n", maxMatch());
	}
	return 0;
}