PAT 数据结构 04-树5. File Transfer (25)

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:

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.
/*2015.7.11*/// 图的连通及优化，7月20日才知道这是并查集#include <iostream>using namespace std;int root[10002];//这么写会超时。。。//int findroot(int a){//if(root[a]!=a)//a=findroot(root[a]);//return a;//}int findroot(int a){if(root[a]!=a)root[a]=findroot(root[a]);////路径压缩，更新为根结点的子结点return root[a];}int main(){int N;scanf("%d",&N);for(int i=1;i<=N;i++)root[i]=i;   //记录每个结点所能连接到的最大节点序号char ch;int a,b;scanf("%c",&ch);while(ch!='S'){scanf("%d%d",&a,&b);if(ch=='I'){int ar=findroot(a);int br=findroot(b);if(ar!=br){N--;if(ar<br)root[ar]=br;elseroot[br]=ar;}}if(ch=='C'){if(findroot(a)==findroot(b)){printf("yes\n");}elseprintf("no\n");}scanf("%c",&ch);}if(N==1)printf("The network is connected.\n");elseprintf("There are %d components.\n",N);return 0;}