We have a network of computers and a list of bi-directional connections. Each of these connections allows a file transfer from one computer to another. Is it possible to send a file from any computer on the network to any other?

Input Specification:

Each input file contains one test case. For each test case, the first line contains N (2≤N≤10​4​​), the total number of computers in a network. Each computer in the network is then represented by a positive integer between 1 and N. Then in the following lines, the input is given in the format:

I c1 c2  

where I stands for inputting a connection between c1 and c2; or

C c1 c2    

where C stands for checking if it is possible to transfer files between c1 and c2; or

S

where S stands for stopping this case.

Output Specification:

For each C case, print in one line the word "yes" or "no" if it is possible or impossible to transfer files between c1

and c2, respectively. At the end of each case, print in one line "The network is connected." if there is a path between any pair of computers; or "There are k components." where k is the number of connected components in this network.

Sample Input 1:

5
C 3 2
I 3 2
C 1 5
I 4 5
I 2 4
C 3 5
S

Sample Output 1:

no
no
yes
There are 2 components.

Sample Input 2:

5
C 3 2
I 3 2
C 1 5
I 4 5
I 2 4
C 3 5
I 1 3
C 1 5
S

Sample Output 2:

no
no
yes
yes
The network is connected.

 程式碼如下：

/*
並查集的查詢與合併
一開始初始化集合的個數為n個..
然後每兩個集合合併就將集合數減一..
最後判斷集合個數是否為一來判定是否兩兩相互連線...
*/
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
using namespace std;
const int maxn=10005;
int n;
int a[maxn];
int num;
char op[5];
void init()
{
    num=n;
    for (int i=1;i<=n;i++)
    {
        a[i]=i;
    }
}
int Find(int x)
{
    if(a[x]==x)
        return x;
    else
        return a[x]=Find(a[x]);
}
void unit(int x,int y)
{
    int px=Find(x);
    int py=Find(y);
    if(px!=py)
    {
       a[px]=py;
       num--;
    }
}
int main()
{
    scanf("%d",&n);
    init();
    while (scanf("%s",op)&&op[0]!='S')
    {
        int x,y;
        scanf("%d%d",&x,&y);
        if(op[0]=='I')
        {
           unit(x,y);
        }
        else
        {
            if(Find(x)==Find(y))
            {
                printf("yes\n");
            }
            else
              printf("no\n");
        }
    }
    if(num==1)
        printf("The network is connected.\n");
    else
        printf("There are %d components.\n",num);
    return 0;
}