File Transfer（25 分）

05-树8 File Transfer（25 分）

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 kcomponents." where k is the number of connected components in this network.

Sample Input 1:

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

Sample Output 1:

nonoyesThere are 2 components.

Sample Input 2:

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

Sample Output 2:

nonoyesyesThe network is connected.

本题还可以做路径压缩等优化，本人并没有，请见陈 越老师详解

#include<iostream>

#include<vector>
using namespace std;
struct node{
int data;
int parent=-1;
};
int size;
int Find(vector<node> &set,int data){
int q=data-1;
while(set[q].parent>0)
q=set[q].parent;
return q; 
}
void connect(vector<node> &set,int i,int j){
int m=Find(set,i);
int n=Find(set,j);
if(set[m].parent<set[n].parent){
    set[m].parent+=set[n].parent; set[n].parent=m;
}
else {set[n].parent+=set[m].parent; set[m].parent=n;}
}
void query(vector<node> &set,int i,int j){
int m=Find(set,i); int n=Find(set,j);
if(m==n) cout<<"yes"<<endl;
else cout<<"no"<<endl;
}
int main(){
   int i=1,j,num; cin>>size; 
   num=size;
   vector<node> set(size);
   for(int p=0;p<size;p++)
   set[p].data=p+1;
   string str; cin>>str;
   while(str!="S"){
    if(str=="C"){
    cin>>i>>j;
    query(set,i,j);
   }
else{
cin>>i>>j;
connect(set,i,j);
num--;
}
cin>>str;
   }
   if(num==1)
   cout<<"The network is connected."<<endl;
   else
   cout<<"There are "<<num<<" components."<<endl;
   return 0;
}