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), 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.
这道题挺基础的,考察并查集
1 #include <cstdio> 2 #include <algorithm> 3 4 using namespace std; 5 6 int father[10001]; 7 int isroot[10001]; 8 9 int findfather(int X) 10 { 11 int R; 12 if(X!=father[X]) 13 R=findfather(father[X]); 14 else R=X; 15 father[X]=R; 16 return R; 17 } 18 19 int main() 20 { 21 int n; 22 scanf("%d",&n); 23 getchar(); 24 for(int i=1;i<=n;i++) 25 { 26 father[i]=i; 27 } 28 char C; 29 while(scanf("%c",&C)&&C!='S') 30 { 31 int a,b,FA,FB; 32 scanf("%d %d",&a,&b); 33 if(C=='I') 34 { 35 FA=findfather(a); 36 FB=findfather(b); 37 if(FA!=FB) 38 father[FA]=FB; 39 } 40 if(C=='C') 41 { 42 FA=findfather(a); 43 FB=findfather(b); 44 if(FA==FB) 45 printf("yes\n"); 46 else 47 printf("no\n"); 48 } 49 } 50 for(int i=1;i<=n;i++) 51 { 52 if(i==findfather(i)) 53 isroot[i]=1; 54 } 55 int num=0; 56 for(int i=1;i<=n;i++) 57 { 58 if(isroot[i]) 59 num++; 60 } 61 if(num!=1) 62 printf("There are %d components.\n",num); 63 else 64 printf("The network is connected.\n"); 65 return 0; 66 }