Algorithms on graphs week 5 Connecting points solution

[unknown-08]

#include<bits/stdc++.h>
#define pb push_back
#define pf push_front
#define mp make_pair
#define ll long long
#define fi first
#define se second
#define mod 1000000007
using namespace std;
bool sortbysec(const pair<int,int> &a,
const pair<int,int> &b)
{
return (a.second < b.second);
}
struct hash_pair {
template <class T1, class T2>size_t operator()(const pair<T1, T2>& p) const
{
auto hash1 = hash{}(p.first);
auto hash2 = hash{}(p.second);
return hash1 ^ hash2;
}
};

bool sortbyth(const tuple<int, int, double>& a,const tuple<int, int, double>& b)
{
return (get<2>(a) < get<2>(b));
}

struct edge{
int a,b;
double cost;
};

double dis(double x1,double y1,double x2,double y2)
{
double d=sqrt((x1-x2)(x1-x2)+(y1-y2)(y1-y2));
return d;
}

class DisjSet {
int *rank, *parent, n;

public:
DisjSet(int n)
{
rank = new int[n];
parent = new int[n];
this->n = n;
makeSet();
}

void makeSet() 
{ 
    for (int i = 0; i < n; i++) { 
        parent[i] = i; 
    } 
} 

int find(int x) 
{ 
    if (parent[x] != x) { 

        parent[x] = find(parent[x]); 
    } 

    return parent[x]; 
} 

void Union(int x, int y) 
{ 
    int xset = find(x); 
    int yset = find(y); 

    if (xset == yset) 
        return; 

    if (rank[xset] < rank[yset]) { 
        parent[xset] = yset; 
    } 
    else if (rank[xset] > rank[yset]) { 
        parent[yset] = xset; 
    } 

    else { 
        parent[yset] = xset; 
        rank[xset] = rank[xset] + 1; 
    } 
} 

};

int main()
{

 #ifdef _DEBUG
 freopen("input.txt", "r", stdin);
 //	freopen("output.txt", "w", stdout);
 #endif
 ios_base::sync_with_stdio(false); 
 cin.tie(NULL);  

int n,i,j;
cin>>n;
double x[n],y[n];
for(i=0;i<n;i++) cin>>x[i]>>y[i];

vector<tuple<int,int,double>>v; // vector tuple used to store the distance between the given points

DisjSet obj(n+1);

for(i=0;i<n;i++)
{
for(j=i+1;j<n;j++)
{
double d=dis(x[i],y[i],x[j],y[j]); // calculating the distance between two points
v.pb(make_tuple(i,j,d)); // storing distance between point i and j in the vector
}
}

sort(v.begin(),v.end(),sortbyth);     // sortng according to the distance 
double ans=0;

for(i=0;i<v.size();i++)
{
   if(obj.find(get<0>(v[i]))!=obj.find(get<1>(v[i])))  // if i and j are not connected yet then connect them
   {
      ans+=get<2>(v[i]);
      obj.Union(get<0>(v[i]),get<1>(v[i]));    
   }
}
printf("%.7lf",ans);

return 0;

}