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temp.cpp
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temp.cpp
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#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cassert>
#include <vector>
#include <cmath>
using std::vector;
using std::pair;
using namespace std;
vector<int> super_set;
void make_set(int i) {
super_set[i] = i;
}
int find_id(int i) {
while (i != super_set[i]) {
i = super_set[i];
}
return i;
}
int parent(int i) {
while (i != super_set[i]) {
i = super_set[i];
}
return i;
}
void union_set(int u, int v) {
int id1 = find_id(u);
int id2 = find_id(v);
if (id1 == id2) return;
super_set[parent(v)] = id1;
}
double clustering(vector<int> x, vector<int> y, int k) {
//write your code here
/*
* use kruskal alogorithm;
* now we have n subset and each subset have one vertices and we want to reduce our subset in to k subset;
* for that i will calculate the distance of each one of them from one another and sort the distance
* increasing order and then union the least distance sub-set up to we will reach the total k subets;
*/
int n = x.size();
std::vector<pair<double, pair<int, int>>> dist; //first store the distance and pair store the vertices
for (int i = 0;i < n;i++) {
for (int j = 0;j < n;j++) {
if (i == j) continue;
double x_ = abs(x[i] - x[j]);
double y_ = abs(y[i] - y[j]);
double d = x_ * x_ + y_ * y_;
d = pow(d, 0.5);
dist.push_back({ d,{i,j} });
}
}
super_set.resize(n);
for (int i = 0;i < n;i++) {
make_set(i);
}
sort(begin(dist), end(dist), [&](pair<double, pair<int, int>>& a, pair<double, pair<int, int>>& b)
{return a.first < b.first; });
int count = n;
for (int i = 0;i < dist.size();i++) {
if (n == k) break;
pair<double, pair<int, int>> top = dist[i];
pair<int, int> ver = top.second;
int u = ver.first; int v = ver.second;
if (find_id(u) == find_id(v)) continue;
//union this;
union_set(u, v);
n--;
/* int g = 0;
for (auto it : super_set) {
cout << g << " : " << it << " \n";
g++;
}
cout << "now next part" << "\n";
*/
} double min_ = 100000.00;
n = dist.size();
for (int i = 0;i < n;i++) {
pair<double, pair<int, int>> top = dist[i];
pair<int, int> ver = top.second;
double d = top.first;
int u = ver.first; int v = ver.second;
if (find_id(u) != find_id(v)) {
min_ = min(min_, d);
}
}
return min_;
}
int main() {
size_t n;
int k;
std::cin >> n;
vector<int> x(n), y(n);
for (size_t i = 0; i < n; i++) {
std::cin >> x[i] >> y[i];
}
std::cin >> k;
std::cout << std::setprecision(10) << clustering(x, y, k) << std::endl;
}