Deficient Numbers.cpp

// C++ program to implement an Optimized Solution
// to check Deficient Number
#include <bits/stdc++.h>
using namespace std;
 
// Function to calculate sum of divisors
int divisorsSum(int n)
{
    int sum = 0; // Initialize sum of prime factors
 
    // Note that this loop runs till square root of n
    for (int i = 1; i <= sqrt(n); i++) {
        if (n % i == 0) {
            // If divisors are equal, take only one
            // of them
            if (n / i == i) {
                sum = sum + i;
            }
            else // Otherwise take both
            {
                sum = sum + i;
                sum = sum + (n / i);
            }
        }
    }
    return sum;
}
 
// Function to check Deficient Number
bool isDeficient(int n)
{
    // Check if sum(n) < 2 * n
    return (divisorsSum(n) < (2 * n));
}
 
/* Driver program to test above function */
int main()
{   int n ;
    cin >> n;
    for (int i = 0; i< n; i++){
      if (isDeficient(i)){
        cout << i << ' ';
      }
    }
 
    return 0;
}