Pairing Hackerrank test case

#1

On hackerrank, 1 test case in not passing .


This is the test case:
Input :
100000 2
1 2
3 4

Output:
4999949998

Check out.

#2 
#include <bits/stdc++.h>
using namespace std;

class Graph{
    long int V;
    list<pair<int,int>> l;
public:
    Graph(long int V){
        this->V = V;
    }

    void addEdge(int u, int v){
        l.push_back(make_pair(u,v));
    }

    int find(int i, int parent[]) {
        if(parent[i]==-1){
            return i;
        }
        return parent[i] = find(parent[i],parent);
    }

    void unionSet(int x, int y, int parent[], int rank[]) {
        int s1 = find(x,parent);
        int s2 = find(y,parent);

        if(s1!=s2){
            if(rank[s1]<rank[s2]){
                parent[s1] = s2;
                rank[s2] += rank[s1];
            }
            else{
                parent[s2] = s1;
                rank[s1] += rank[s2];
            }
        }
    }

    int pairing(){
        int *parent = new int[V];
        int *rank = new int[V];

        for(int i=0;i<V;i++){
            parent[i] = -1;
            rank[i] = 1;
        }

        for(auto edge:l){
            int i = edge.first;
            int j = edge.second;

            int s1 = find(i,parent);
            int s2 = find(j,parent);

            unionSet(s1,s2,parent,rank);
        }

        long long int ans=0;
        for(long int i=0;i<V;i++){
            ans += V - rank[find(i,parent)];
        }

        return ans/2;
    }
};

int main(){
    long int n,p;
    cin>>n>>p;
    Graph g(n);
    while(p--) {
        int u,v;
        cin>>u>>v;
        g.addEdge(u,v);
    }
    cout<<g.pairing()<<endl;
    return 0;
}
#3

@anishanand3733,
Is this input giving correct output?

Input
10 2
1 2
3 4

#4

Yes, getting correct output for this.

#5

@anishanand3733,
Initialize parent[i]=i;