zoukankan      html  css  js  c++  java
  • POJ——T 1422 Air Raid

    http://poj.org/problem?id=1422

    Time Limit: 1000MS   Memory Limit: 10000K
    Total Submissions: 8579   Accepted: 5129

    Description

    Consider a town where all the streets are one-way and each street leads from one intersection to another. It is also known that starting from an intersection and walking through town's streets you can never reach the same intersection i.e. the town's streets form no cycles. 

    With these assumptions your task is to write a program that finds the minimum number of paratroopers that can descend on the town and visit all the intersections of this town in such a way that more than one paratrooper visits no intersection. Each paratrooper lands at an intersection and can visit other intersections following the town streets. There are no restrictions about the starting intersection for each paratrooper. 

    Input

    Your program should read sets of data. The first line of the input file contains the number of the data sets. Each data set specifies the structure of a town and has the format: 

    no_of_intersections 
    no_of_streets 
    S1 E1 
    S2 E2 
    ...... 
    Sno_of_streets Eno_of_streets 

    The first line of each data set contains a positive integer no_of_intersections (greater than 0 and less or equal to 120), which is the number of intersections in the town. The second line contains a positive integer no_of_streets, which is the number of streets in the town. The next no_of_streets lines, one for each street in the town, are randomly ordered and represent the town's streets. The line corresponding to street k (k <= no_of_streets) consists of two positive integers, separated by one blank: Sk (1 <= Sk <= no_of_intersections) - the number of the intersection that is the start of the street, and Ek (1 <= Ek <= no_of_intersections) - the number of the intersection that is the end of the street. Intersections are represented by integers from 1 to no_of_intersections. 

    There are no blank lines between consecutive sets of data. Input data are correct. 

    Output

    The result of the program is on standard output. For each input data set the program prints on a single line, starting from the beginning of the line, one integer: the minimum number of paratroopers required to visit all the intersections in the town. 

    Sample Input

    2
    4
    3
    3 4
    1 3
    2 3
    3
    3
    1 3
    1 2
    2 3

    Sample Output

    2
    1

    Source

     
    最短路径覆盖==总点数-最大匹配数
     1 #include <cstring>
     2 #include <cstdio>
     3 
     4 using namespace std;
     5 
     6 int n,map[123][123],match[123];
     7 bool vis[123];
     8 
     9 bool find(int u)
    10 {
    11     for(int v=1;v<=n;v++)
    12         if(map[u][v]&&!vis[v])
    13         {
    14             vis[v]=1;
    15             if(!match[v]||find(match[v]))
    16             {
    17                 match[v]=u;
    18                 return true;
    19             }
    20         }
    21     return false;
    22 }
    23 
    24 int AC()
    25 {
    26     int t;scanf("%d",&t);
    27     for(int m,ans;t--;)
    28     {
    29         scanf("%d%d",&n,&m);ans=n;
    30         for(int u,v;m--;map[u][v]=1)
    31             scanf("%d%d",&u,&v);
    32         for(int i=1;i<=n;i++)
    33         {
    34             memset(vis,0,sizeof(vis));
    35             if(find(i)) ans--;
    36         }
    37         printf("%d
    ",ans);
    38         memset(map,0,sizeof(map));
    39         memset(match,0,sizeof(match));
    40     }
    41     return 0;
    42 }
    43 
    44 int I_want_AC=AC();
    45 int main(){;}
    ——每当你想要放弃的时候,就想想是为了什么才一路坚持到现在。
  • 相关阅读:
    负载均衡,分布式,集群的理解,多台服务器代码如何同步
    浅谈控制反转与依赖注入
    Jetbrains系列产品重置试用方法
    讲述一下一个还没毕业的科班程序猿的求职历程
    一个在求职路上挣扎的萌新
    用C#操作文件/文件夹(删除,复制,移动)
    随笔-关于公网IP无法访问服务器的解决办法
    C/s从文件(TXT)中读取数据插入数据库
    Sql Server + ADO.NET
    进程。线程与线程池
  • 原文地址:https://www.cnblogs.com/Shy-key/p/7424322.html
Copyright © 2011-2022 走看看