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 

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.

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
.parent){

    set[m].parent+=set
.parent; set
.parent=m;
}
else {set
.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;

}