05-树8 File Transfer (25分)

最新推荐文章于 2020-06-03 15:46:09 发布

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本文探讨了如何使用并查集解决计算机网络中文件传输路径的问题。通过输入一系列的连接和查询指令，程序能够判断任意两台计算机间是否可以进行文件传输，并最终评估整个网络的连通性。

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 $N$ ( $2\le N\le 10^4$ ), 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 c1and c2; or

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 kis the number of connected components in this network.

Sample Input 1:

Sample Output 1:

no
no
yes
There are 2 components.

Sample Input 2:

Sample Output 2:

no
no
yes
yes
The network is connected.

解：这是一个可以利用并查集的一个问题，集合的合并与查找

代码：

/*
 *并查集问题
 */
#include <iostream>
#include <vector>
using namespace std;
const int maxlen = 10001;
int find_set(vector<int> &set, int data){
	while(set[data] > 0){
		data = set[data];
	}
	return data;
}
void union_set(vector<int> &set, int data1, int data2){
	int index1 = find_set(set, data1);
	int index2 = find_set(set, data2);
	if(set[index1] < set[index2]){
		set[index2] = index1;
		set[index1]--;
	}else{
		set[index1] = index2;
		set[index2]--;
	}
}
bool check_set(vector<int> &set, int data1, int data2){
	int index1 = find_set(set, data1);
	int index2 = find_set(set, data2);
	if(index1 == index2){
		return true;
	}else{
		return false;
	}
}
int count_set(vector<int> &set){
	int num = 0;
	for(unsigned int i = 1; i < set.size(); i++){
		if(set[i] < 0){
			num++;
		}
	}
	return num;
}
int main(){
	int N;
	cin>>N;
	vector<int> set(N + 1);
	for(int i = 1; i <= N; i++){
		set[i] = -1;
	}
	char str;
	int data1 = 0, data2 = 0;
	while(1){
		cin>>str;
		if(str == 'S'){
			break;
		}else if(str == 'I'){
			cin>>data1>>data2;
			union_set(set, data1, data2);
		}else{
			cin>>data1>>data2;
			if(check_set(set, data1, data2)){
				cout<<"yes"<<endl;
			}else{
				cout<<"no"<<endl;
			}
		}
	}
	int num = count_set(set);
	if(num > 1){
		cout<<"There are "<<num<<" components."<<endl;
	}else{
		cout<<"The network is connected.";
	}
}