习题7-1(uva-208)

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本文介绍了一段使用C++编写的代码，通过并查集实现查找父子关系，并利用深度优先搜索(DFS)找出从消防站到街角的所有可能路径。程序读取输入数据，维护图的连通性和路径，最后输出路线数量。

#include <iostream>
#include <istream>
#include <sstream>
#include <vector>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <numeric>
#include <chrono>
#include <ctime>
#include <cmath>
#include <cctype>
#include <string>
#include <cstdio>
#include <iomanip>


#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <iterator>
using namespace std;

const int maxn = 21;
int last,vis[maxn];
vector<int> matrix[maxn];
vector<vector<int> > ret;

int family[maxn];

int GetFather(int a){
	return family[a] != a ? a = GetFather(family[a]) : a;
}
void AddOne(int a, int b){
	int fa = GetFather(a);
	int fb = GetFather(b);
	if (fa != fb) family[fa] = family[fb];
}

void dfs(vector<int> &temp,int cur){
	temp.push_back(cur);
	vis[cur] = 1;
	if (cur == last){
		ret.emplace_back(temp);
		temp.pop_back();
		vis[cur] = 0;
		return;
	}
	for (int i = 0; i < matrix[cur].size(); i++){
		if (vis[matrix[cur][i]]) continue;
		dfs(temp, matrix[cur][i]);
	}
	vis[cur] = 0;
	temp.pop_back();
}

int main(){
	int a, b,id = 0;
	vector<int> temp;
	while (cin >> last){

		for (int i = 0; i < maxn; i++) {
			matrix[i].clear();
			family[i] = i;
		}
		memset(vis, 0, sizeof(vis));
		ret.clear();
		
		while (cin >> a >> b && a&&b){
			matrix[a].push_back(b);
			matrix[b].push_back(a);
			AddOne(a, b);
		}
		for (int i = 0; i < maxn; i++) {
			sort(matrix[i].begin(), matrix[i].end());
		}
		if (GetFather(1) == GetFather(last))
			dfs(temp,1);
		cout << "CASE " << ++id << ":" << endl;

		for (int i = 0; i < ret.size(); i++){
			for (int j = 0; j < ret[i].size(); j++){
				if (j) cout << " ";
				cout << ret[i][j];
			}
			cout << endl;
		}
		cout << "There are " << ret.size() << " routes from the firestation to streetcorner " << last << "." << endl;
	}
	return 0;
}