zoukankan      html  css  js  c++  java
  • Hdu 1045 二分匹配

    题目链接

    Fire Net

    Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
    Total Submission(s): 6282    Accepted Submission(s): 3551


    Problem 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
    使用建图技巧:一行变多行,一列变多列。这样就可以消除墙的作用。1A
    Accepted Code:
     1 /*************************************************************************
     2     > File Name: 1045.cpp
     3     > Author: Stomach_ache
     4     > Mail: sudaweitong@gmail.com
     5     > Created Time: 2014年08月01日 星期五 23时01分49秒
     6     > Propose: 
     7  ************************************************************************/
     8 #include <queue>
     9 #include <cmath>
    10 #include <string>
    11 #include <cstdio>
    12 #include <fstream>
    13 #include <cstring>
    14 #include <iostream>
    15 #include <algorithm>
    16 using namespace std;
    17 
    18 char map[5][5];
    19 int cx[50], cy[50];
    20 int row[5][5], col[5][5];
    21 bool mark[50];
    22 int G[50][50];
    23 int n, cnt1, cnt2;
    24 
    25 int path(int u) {
    26       for (int i = 1; i < cnt2; i++) {
    27           if (G[u][i] && !mark[i]) {
    28               mark[i] = true;
    29             if (cy[i] == -1 || path(cy[i])) {
    30                   cy[i] = u;
    31                 cx[u] = i;
    32                 return 1;
    33             }
    34         }
    35     }
    36     return 0;
    37 }
    38 
    39 int MaxMatch() {
    40       memset(cx, -1, sizeof(cx));
    41     memset(cy, -1, sizeof(cy));
    42     int res = 0;
    43     for (int i = 1; i < cnt1; i++) {
    44           if (cx[i] == -1) {
    45               memset(mark, false, sizeof(mark));
    46               res += path(i);
    47         }
    48     }
    49     return res;
    50 }
    51 
    52 int main(void) {
    53       while (~scanf("%d", &n) && n) {
    54           for (int i = 0; i < n; i++) {
    55               scanf("%s", map[i]);
    56         }
    57         cnt1 = 1;
    58         for (int i = 0; i < n; i++) {
    59               for (int j = 0; j < n; j++) {
    60                   col[i][j] = cnt1;
    61                 if (j == n-1 || map[i][j] == 'X') cnt1++;
    62             }
    63         }
    64         cnt2 = 1;
    65         for (int i = 0; i < n; i++) {
    66               for (int j = 0; j < n; j++) {
    67                   row[j][i] = cnt2;
    68                 if (j == n-1 || map[j][i] == 'X') cnt2++;
    69             }
    70         }
    71         memset(G, 0, sizeof(G));
    72         for (int i = 0; i < n; i++) 
    73               for (int j = 0; j < n; j++) if (map[i][j] != 'X') {
    74                   G[row[i][j]][col[i][j]] = 1;
    75             }
    76         printf("%d
    ", MaxMatch());
    77     }
    78 
    79     return 0;
    80 }
  • 相关阅读:
    java中构造器的使用
    Java包装类
    Linux TOP命令 按内存占用排序和按CPU占用排序 分类: 测试 ubuntu 虚拟机 2013-11-06 14:38 396人阅读 评论(0) 收藏
    多态 分发 分类: python 小练习 divide into python 2013-11-05 19:11 394人阅读 评论(0) 收藏
    #小练习 输出模块中方法及其docstring 分类: python 小练习 divide into python 2013-11-05 18:17 451人阅读 评论(0) 收藏
    #小练习 重定向与sys.stdout对象 分类: python 小练习 2013-11-05 16:10 437人阅读 评论(0) 收藏
    #小练习 类与文件对象 分类: python 小练习 2013-11-05 15:39 343人阅读 评论(0) 收藏
    #小练习类与文件对象 分类: python 小练习 2013-11-05 12:09 341人阅读 评论(0) 收藏
    if ...__name__使用技巧总结 分类: python基础学习 python Module python 2013-11-01 14:51 262人阅读 评论(0) 收藏
    使用urllib2解析html内容,并正常显示中文的方法 分类: python Module 2013-10-31 17:30 294人阅读 评论(0) 收藏
  • 原文地址:https://www.cnblogs.com/Stomach-ache/p/3886015.html
Copyright © 2011-2022 走看看