UVA_10397_Connect the Campus

#include<iostream>    
#include<sstream>    
#include<string>    
#include<vector>    
#include<list>    
#include<set>    
#include<map>    
#include<stack>    
#include<queue>    
#include<algorithm>    
#include<cmath>    
#pragma warning(disable:4996)    
using std::cin;
using std::cout;
using std::endl;
using std::stringstream;
using std::string;
using std::vector;
using std::list;
using std::pair;
using std::set;
using std::multiset;
using std::map;
using std::multimap;
using std::stack;
using std::queue;
using std::sort;
class DisjoinSet
{
private:
	vector<int>represent, rank;
public:
	DisjoinSet(const int &n) :represent(n), rank(n)
	{
		for (int i = 0; i < n; i++)
		{
			represent[i] = i;
		}
	}
	int find(int i)
	{
		return represent[i] = represent[i] == i ? i : find(represent[i]);
	}
	void merge(const int &x, const int &y)
	{
		auto a = find(x); auto b = find(y);
		if (rank[a] < rank[b])
		{
			represent[a] = b;
		}
		else
		{
			represent[b] = a;
			if (rank[b] == rank[a])
			{
				rank[a]++;
			}
		}
	}
};
class Edge
{
public:
	pair<int, int>vertex;
	double weight;
	Edge(const pair<int, int>&v, const double &w)
	{
		vertex = v;
		weight = w;
	}
};
bool compare(const Edge&a, const Edge&b)
{
	if (a.weight != b.weight)
	{
		return a.weight < b.weight;
	}
	if (a.vertex.first != b.vertex.first)
	{
		return a.vertex.first < b.vertex.first;
	}
	return a.vertex.second < b.vertex.second;
}
vector<Edge>getEdge()
{
	int n; 
	if (cin >> n)
	{
		;
	}
	else
	{
		exit(0);
	}
	vector<pair<double, double>>vertex(n);
	vector<vector<double>>graph(n,(vector<double>)n);
	for (int i = 0; i < n; i++)
	{
		cin >> vertex[i].first >> vertex[i].second;
	}
	for (int i = 0; i < n; i++)
	{
		for (int j = i+1; j < n; j++)
		{
			graph[i][j] = graph[j][i] = sqrt(pow(vertex[i].first - vertex[j].first, 2) + pow(vertex[i].second - vertex[j].second, 2));
		}
	}
	cin >> n;
	while (n--)
	{
		int first, second;
		cin >> first >> second;
		graph[first - 1][second - 1] = graph[second - 1][first - 1] = 0.0;
	}
	vector<Edge>edge;
	for (int i = 0; i < vertex.size(); i++)
	{
		for (int j = i + 1; j < vertex.size(); j++)
		{
			edge.push_back({{ i,j }, graph[i][j]});
		}
	}
	sort(edge.begin(), edge.end(), compare);
	return edge;
}
double kruscal(const vector<Edge>&edge)
{
	DisjoinSet union_set((int)sqrt(edge.size() * 2) + 1);
	double sum = 0;
	int block = (int)sqrt(edge.size() * 2) + 1;
	for (size_t i = 0; i < edge.size(); i++)
	{
		if (union_set.find(edge[i].vertex.first) != union_set.find(edge[i].vertex.second))
		{
			union_set.merge(edge[i].vertex.first, edge[i].vertex.second);
			sum += edge[i].weight;
			block--;
			if (block == 1)
			{
				return sum;
			}
		}
	}
	return 0;
}
int main()
{
	//freopen("input.txt","r",stdin);    
	//freopen("output.txt","w",stdout);
	while (1)
	{
		auto edge = getEdge();
		printf("%.2lf\n",kruscal(edge));
	}
	return 0;
}