GT havel hakimi

 //Havel-Hakimi theorem

#include <bits/stdc++.h>

#include <iostream>

#include <vector>

using namespace std;

bool test(vector<int> arr){

 while(1){

 sort(arr.rbegin(), arr.rend());

 if(arr[0] == 0){

 return true;

 }

 if(arr[0] > arr.size()-1){

 return false;

 }

 for(int i = 1; i<arr[0] ; i++){

 arr[i]--;

 if (arr[i] < 0){

 return false;

 }

 }

 arr[0] = 0;

 }

 return true;

}

int main(){

 int n,i=1;

 while(i){

 cout << " Enter number of Nodes : ";

 cin >> n;

 vector<int> arr(n);

 cout << " Enter Array : ";

 int sum = 0;

 for(int i=0; i<n ;i++){

 cin >> arr[i];

 sum += arr[i];

 }

 if(sum%2==0 && test(arr)){

 cout << " Possible to Make graph : " << endl;

 }

 else{

 cout << " Not Possible to Make graph : " <<endl;

 }

 cout<<"Enter 1 for continue and 0 for exit \n ";

 cin>>i;

 }

 return 0;

}