7-8 File Transfer (25 分)(c++)(並查集)
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≤104), 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:
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
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.
#include <iostream>
#include <algorithm>
#include <cstdio>
#include <vector>
#include <stack>
#include <cmath>
using namespace std;
const int maxn=10010;
vector<int> father(maxn,-1);
int findFather(int n){
if(father[n]==-1) return n;
else{
int f=findFather(father[n]);
father[n]=f;
return f;
}
}
void uni(int a,int b){
int fa=findFather(a);
int fb=findFather(b);
if(fa!=fb) father[fa]=fb;
}
void check(int a,int b){
if(findFather(a)==findFather(b)) cout<<"yes"<<endl;
else cout<<"no"<<endl;
}
int main()
{
int n,cnt=0;
cin>>n;
char s;
cin>>s;
while(s!='S'){
int a,b;
cin>>a>>b;
if(s=='C'){
check(a, b);
}else if(s=='I'){
uni(a,b);
}
cin>>s;
}
for(int j=1;j<=n;j++){
if(father[j]==-1) cnt++;
}
if(cnt==1) cout<<"The network is connected."<<endl;
else cout<<"There are "<<cnt<<" components."<<endl;
return 0;
}