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:
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.
code
# include <iostream>
# include <cstdio>
struct set {
int n;
int * root;
set(int _n):n(_n)
{
root = new int[n+1];
for (int i = 1; i <= n; ++i) root[i] = -1;
}
void u(int a, int b) //并
{
root[f(a)] = f(b);
}
bool f(int a, int b) //查
{
return f(a) == f(b);
}
int f(int a) //查根
{
if (root[a] == -1) return a;
return root[a] = f(root[a]);
}
int s(void)
{
int ans = 0;
for (int i = 1; i <= n; ++i)
{
if (root[i] == -1) ans++;
}
return ans;
}
};
int main(void)
{
int n;
scanf("%d", &n);
char op;
set s(n);
do
{
int a, b;
scanf("\n%c", &op);
switch (op)
{
case 'C':
scanf("%d%d", &a, &b);
if (s.f(a, b)) printf("yes\n");
else printf("no\n");
break;
case 'I':
scanf("%d%d", &a, &b);
s.u(a, b);
break;
case 'S':
int tmp = s.s();
if (tmp == 1) printf("The network is connected.\n");
else printf("There are %d components.\n", tmp);
}
} while (op != 'S');
return 0;
}