zoukankan      html  css  js  c++  java
  • Brain Network (easy)(并查集水题)

    G - Brain Network (easy)

    Time Limit:2000MS     Memory Limit:262144KB     64bit IO Format:%I64d & %I64u

    CodeForces 690C1

    Description

    One particularly well-known fact about zombies is that they move and think terribly slowly. While we still don't know why their movements are so sluggish, the problem of laggy thinking has been recently resolved. It turns out that the reason is not (as previously suspected) any kind of brain defect – it's the opposite! Independent researchers confirmed that the nervous system of a zombie is highly complicated – it consists of n brains (much like a cow has several stomachs). They are interconnected by brain connectors, which are veins capable of transmitting thoughts between brains. There are two important properties such a brain network should have to function properly:

    1. It should be possible to exchange thoughts between any two pairs of brains (perhaps indirectly, through other brains).
    2. There should be no redundant brain connectors, that is, removing any brain connector would make property 1 false.

    If both properties are satisfied, we say that the nervous system is valid. Unfortunately (?), if the system is not valid, the zombie stops thinking and becomes (even more) dead. Your task is to analyze a given nervous system of a zombie and find out whether it is valid.

    Input

    The first line of the input contains two space-separated integers n and m (1 ≤ n, m ≤ 1000) denoting the number of brains (which are conveniently numbered from 1 to n) and the number of brain connectors in the nervous system, respectively. In the next m lines, descriptions of brain connectors follow. Every connector is given as a pair of brains ab it connects (1 ≤ a, b ≤ na ≠ b).

    Output

    The output consists of one line, containing either yes or no depending on whether the nervous system is valid.

    Sample Input

    Input
    4 4
    1 2
    2 3
    3 1
    4 1
    Output
    no
    Input
    6 5
    1 2
    2 3
    3 4
    4 5
    3 6

    Output

    yes

    //并查集水题,第一行 n , m 是点,和边个数,然后 m 边的描述,问是否都连通了且没有多余的边

     1 #include<stdio.h>
     2 int f[1001];
     3 int find(int x)
     4 {
     5     if (f[x]!=x)
     6         f[x]=find(f[x]);
     7     return f[x];
     8 }
     9 int main()
    10 {
    11     int n,m;
    12     while (scanf("%d%d",&n,&m)!=EOF)
    13     {
    14         int i,j;
    15         for (i=1;i<=n;i++)
    16         f[i]=i;
    17         
    18         int a,b,temp;
    19         scanf("%d%d",&a,&b);
    20         temp=a;
    21         f[a]=f[b];
    22         int ok=1;
    23         for (i=2;i<=m;i++)
    24         {
    25             scanf("%d%d",&a,&b);
    26             int head_a=find(a);
    27             int head_b=find(b);
    28             if (head_a!=head_b)
    29             f[head_a]=f[head_b];
    30             else
    31                 ok=0;
    32         }
    33         for (i=1;i<=n;i++)
    34         {
    35             if (ok==0) break;
    36             if (find(i)!=find(temp))
    37             {
    38             ok=0;
    39             break;
    40             }
    41         }
    42         if (ok)
    43         printf("yes
    ");
    44         else
    45         printf("no
    ");
    46     }
    47     return 0;
    48 }
    View Code
  • 相关阅读:
    myeclipse关掉references
    eclipse/myeclipse SVN资源库URL中文乱码问题解决办法
    获取登录用户ip
    MySQL高级 之 explain执行计划详解(转)
    代码部署工具walle(一)
    mongodb备份策略
    nginx报错整理
    记一次java程序占用cpu超高排查
    HDFS恢复误删操作的方法
    有趣的工具
  • 原文地址:https://www.cnblogs.com/haoabcd2010/p/5924925.html
Copyright © 2011-2022 走看看