Fire Net

Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d & %I64u

Description

Suppose that we have a square city with straight streets. A map of a city is a square board with n rows and n columns, each representing a street or a piece of wall.

A blockhouse is a small castle that has four openings through which to shoot. The four openings are facing North, East, South, and West, respectively. There will be one machine gun shooting through each opening.

Here we assume that a bullet is so powerful that it can run across any distance and destroy a blockhouse on its way. On the other hand, a wall is so strongly built that can stop the bullets.

The goal is to place as many blockhouses in a city as possible so that no two can destroy each other. A configuration of blockhouses is legal provided that no two blockhouses are on the same horizontal row or vertical column in a map unless there is at least one wall separating them. In this problem we will consider small square cities (at most 4x4) that contain walls through which bullets cannot run through.

The following image shows five pictures of the same board. The first picture is the empty board, the second and third pictures show legal configurations, and the fourth and fifth pictures show illegal configurations. For this board, the maximum number of blockhouses in a legal configuration is 5; the second picture shows one way to do it, but there are several other ways.

Your task is to write a program that, given a description of a map, calculates the maximum number of blockhouses that can be placed in the city in a legal configuration.

 

Input

The input file contains one or more map descriptions, followed by a line containing the number 0 that signals the end of the file. Each map description begins with a line containing a positive integer n that is the size of the city; n will be at most 4. The next n lines each describe one row of the map, with a '.' indicating an open space and an uppercase 'X' indicating a wall. There are no spaces in the input file. 
 

Output

For each test case, output one line containing the maximum number of blockhouses that can be placed in the city in a legal configuration.
 

Sample Input

4
.X..
....
XX..
....
2
XX
.X
3
.X.
X.X
.X.
3
...
.XX
.XX
4
....
....
....
....
0
 

Sample Output

5
1
5
2
4

题目大意:给你n*n的矩阵,里面有些位置有墙。要在空地方放上炮弹,导弹会攻击上下左右四个方向,导弹的攻击不能通过墙即碰到墙就停止了。问你最多能在里面放入多少个炮弹。

解题思路:由于有墙的阻隔,所以不能简单地将行列直接分为二部。所以考虑一行中,如果遇到墙,可以认为是已经换行了,让行数加一。同样,列也这样考虑。在我们呢这种意义下的行列有交汇的地方,连一条边。求最大匹配。

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<iostream>
using namespace std;
int vis[110][110], G[110][110], linker[110], used[110];
char Map[110][110];
bool dfs(int u,int _n){
for(int v = 1; v <= _n; v++){
if(G[u][v] && !used[v]){
used[v] = u;
if(linker[v] == -1 || dfs(linker[v],_n)){
linker[v] = u;
return true;
}
}
}
return false;
}
int hungary(int un,int vn){
int ret = 0;
memset(linker,-1,sizeof(linker));
for(int i = 1; i <= un; i++){
memset(used,0,sizeof(used));
if(dfs(i,vn))
ret++;
}
return ret;
}
int main(){
int n;
while(scanf("%d",&n)!=EOF&&n){ for(int i = 1; i <= n; i++){
getchar();
for(int j = 1; j <= n; j++){
scanf("%c",&Map[i][j]);
}
}
memset(vis,0,sizeof(vis));
int vn = 0, flag;
for(int i = 1; i <= n; i++){
flag = 1;
for(int j = 1; j <= n; j++){
if(Map[i][j] == 'X'){
flag = 1;
}else{
if(flag) {
vn++;
flag = 0;
}
vis[i][j] = vn;
}
}
}
memset(G,0,sizeof(G));
int un = 0;
for(int j = 1; j <= n; j++){
flag = 1;
for(int i = 1; i <= n; i++){
if(Map[i][j] == 'X'){
flag = 1;
}else{
if(flag){
un++;
flag = 0;
}
G[un][vis[i][j]] = 1;
}
}
}
int ans = hungary(un,vn);
printf("%d\n",ans);
}
return 0;
}

  

HDU 1045——Fire Net——————【最大匹配、构图、邻接矩阵做法】的更多相关文章

  1. HDOJ(HDU).1045 Fire Net (DFS)

    HDOJ(HDU).1045 Fire Net [从零开始DFS(7)] 点我挑战题目 从零开始DFS HDOJ.1342 Lotto [从零开始DFS(0)] - DFS思想与框架/双重DFS HD ...

  2. hdu 1045 Fire Net(最小覆盖点+构图(缩点))

    http://acm.hdu.edu.cn/showproblem.php?pid=1045 Fire Net Time Limit:1000MS     Memory Limit:32768KB   ...

  3. HDU 1045 Fire Net(图匹配)

    题目大意: 这个是以前做过的一道DFS题目,当时是完全暴力写的. 给你一个N代表是N*N的矩阵,矩阵内 ‘X’代表墙, ‘.’代表通道. 问这个矩阵内最多可以放几个碉堡, 碉堡不能在同一行或者同一列, ...

  4. HDU 1045(Fire Net)题解

    以防万一,题目原文和链接均附在文末.那么先是题目分析: [一句话题意] 给定大小的棋盘中部分格子存在可以阻止互相攻击的墙,问棋盘中可以放置最多多少个可以横纵攻击炮塔. [题目分析] 这题本来在搜索专题 ...

  5. HDU 1045 Fire Net 【连通块的压缩 二分图匹配】

    题目:http://acm.hdu.edu.cn/showproblem.php?pid=1045 Fire Net Time Limit: 2000/1000 MS (Java/Others)    ...

  6. HDU 1045 Fire Net(dfs,跟8皇后问题很相似)

    传送门:http://acm.hdu.edu.cn/showproblem.php?pid=1045 Fire Net Time Limit: 2000/1000 MS (Java/Others)   ...

  7. HDU 1045 Fire Net 状压暴力

    原题链接:http://acm.hdu.edu.cn/showproblem.php?pid=1045 Fire Net Time Limit: 2000/1000 MS (Java/Others)  ...

  8. HDU 1045 Fire Net 二分图建图

    HDU 1045 题意: 在一个n*n地图中,有许多可以挡住子弹的墙,问最多可以放几个炮台,使得炮台不会相互损害.炮台会向四面发射子弹. 思路: 把行列分开做,先处理行,把同一行中相互联通的点缩成一个 ...

  9. HDU 1045 - Fire Net - [DFS][二分图最大匹配][匈牙利算法模板][最大流求二分图最大匹配]

    题目链接:http://acm.split.hdu.edu.cn/showproblem.php?pid=1045 Time Limit: 2000/1000 MS (Java/Others) Mem ...

随机推荐

  1. tomcat的日志文件权限与启动用户的权限不一致

    用户work的文件权限(umask=0002)为 u=rwx,g=rwx,o=rx 但是tomcat的日志文件的权限却是:为什么会不一样呢? 这是因为tomcat在启动(catalina.sh)时会重 ...

  2. CHNS类

    NS类集合介绍 1.常用部分 NSDictionary NSString NSArray 数组 NSTimer 定时器 NSRange 范围 NSNotification 2.网络相关 NSURLCo ...

  3. 51nod1244 莫比乌斯函数之和(杜教筛)

    题面 传送门 题解 我--我忘记把预处理的块的大小调成\(n^{\frac{2}{3}}\)了--(仰天) 首先\(\mu*1=e\) 然后杜教筛就行了 //minamoto #include< ...

  4. echarts图标legend全选功能添加

    平时做图表的时候经常用echarts,确实是一款很好用的插件. 开发中遇到了一个问题,在展示的曲线,也就是legend很多的时候,不太好只展示其中几条.配置中是可以默认设置初始化是否展示,但不适用于全 ...

  5. Python——用os模块寻找指定目录(包括子目录)下所有图片文件

    import os # 导入os模块 def search_file(start_dir): img_list = [] extend_name = ['.jpg', '.png', '.gif'] ...

  6. P1592 互质

    题意:输入两个正整数n和k,求与n互质的第k个正整数. $n≤10^6,k≤10^8$ 可以枚举出互质的数,居然发现,有循环节.... 比如10 与其互质的1  3  7  9  11  13  17 ...

  7. linux 环境下tomcat中部署jfinal项目

    tomcat中部署jfinal项目 问题现象如下图 问题描述: 我在自己的windows7系统上tomcat下面跑这个项目没有任何问题吗,但是当我把项目上传到linux服务器上的tomcatwebap ...

  8. Github常见命令整理

    常见命令: 将文件增加到index/stage暂存区: git add filename 将暂存的文件更新到本地库中:git commit -m "备注内容" 将本地库更新到远程库 ...

  9. poj3274 找平衡数列(哈希加一点数学思维)

    题目传送门 题目大意:有n只牛,每只牛有k个属性,接下来n个数字,每个数字的二进制位上的1和0分别表示某种属性的有或者无,然后一个特殊数列就是,一个区间内所有牛的各种属性的总和相等(有e种1属性  e ...

  10. 1065. A+B and C (64bit) (20)

    Given three integers A, B and C in [-263, 263], you are supposed to tell whether A+B > C. Input S ...