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Check if a number can be expressed as sum two abundant numbers

  • Difficulty Level : Easy
  • Last Updated : 31 May, 2021

Given a number N. The task is to express N as the sum of two Abundant Numbers. If it is not possible, print -1.
 

Examples:

Input : N = 24 
Output : 12, 12

Input : N = 5
Output : -1 

Approach: An efficient approach is to store all abundant numbers in a set. And for a given number, N runs a loop from 1 to n and checks if i and n-i are abundant numbers or not.
Below is the implementation of the above approach: 

C++




// CPP program to check if number n is expressed
// as sum of two abundant numbers
#include <bits/stdc++.h>
using namespace std;
#define N 100005
 
// Function to return all abundant numbers
// This function will be helpful for
// multiple queries
set<int> ABUNDANT()
{
    // To store abundant numbers
    set<int> v;
 
    for (int i = 1; i < N; i++) {
 
        // to store sum of the divisors
        // include 1 in the sum
        int sum = 1;
        for (int j = 2; j * j <= i; j++) {
 
            // if j is proper divisor
            if (i % j == 0) {
                sum += j;
 
                // if i is not a perfect square
                if (i / j != j)
                    sum += i / j;
            }
        }
 
        // if sum is greater than i then i is
        // a abundant number
        if (sum > i)
            v.insert(i);
    }
 
    return v;
}
 
// Check if number n is expressed
// as sum of two abundant numbers
void SumOfAbundant(int n)
{
    set<int> v = ABUNDANT();
 
    for (int i = 1; i <= n; i++) {
 
        // if both i and n-i are
        // abundant numbers
        if (v.count(i) and v.count(n - i)) {
            cout << i << " " << n - i;
            return;
        }
    }
 
    // can not be expressed
    cout << -1;
}
 
// Driver code
int main()
{
    int n = 24;
    SumOfAbundant(n);
    return 0;
}

Java




// Java program to check if number n is expressed
// as sum of two abundant numbers
import java.util.*;
class GFG {
 
    static final int N = 100005;
 
// Function to return all abundant numbers
// This function will be helpful for
// multiple queries
    static Set<Integer> ABUNDANT() {
        // To store abundant numbers
        Set<Integer> v = new HashSet<>();
 
        for (int i = 1; i < N; i++) {
 
            // to store sum of the divisors
            // include 1 in the sum
            int sum = 1;
            for (int j = 2; j * j <= i; j++) {
 
                // if j is proper divisor
                if (i % j == 0) {
                    sum += j;
 
                    // if i is not a perfect square
                    if (i / j != j) {
                        sum += i / j;
                    }
                }
            }
 
            // if sum is greater than i then i is
            // a abundant number
            if (sum > i) {
                v.add(i);
            }
        }
 
        return v;
    }
 
// Check if number n is expressed
// as sum of two abundant numbers
    static void SumOfAbundant(int n) {
        Set<Integer> v = ABUNDANT();
 
        for (int i = 1; i <= n; i++) {
 
            // if both i and n-i are
            // abundant numbers
            if (v.contains(i) & v.contains(n - i)) {
                System.out.print(i + " " + (n - i));
                return;
            }
        }
 
        // can not be expressed
        System.out.print(-1);
    }
 
// Driver code
    public static void main(String[] args) {
        int n = 24;
        SumOfAbundant(n);
    }
}
// This code is contributed by 29AjayKumar

Python 3




# Python 3 program to check if number n is
# expressed as sum of two abundant numbers
 
# from math lib import sqrt function
from math import sqrt
 
N = 100005
 
# Function to return all abundant numbers
# This function will be helpful for
# multiple queries
def ABUNDANT() :
 
    # To store abundant numbers
    v = set() ;
 
    for i in range(1, N) :
 
        # to store sum of the divisors
        # include 1 in the sum
        sum = 1
        for j in range(2, int(sqrt(i)) + 1) :
             
            # if j is proper divisor
            if (i % j == 0) :
                sum += j
                 
            # if i is not a perfect square
            if (i / j != j) :
                sum += i // j
                 
        # if sum is greater than i then i
        # is a abundant numbe
        if (sum > i) :
            v.add(i)
     
    return v
 
# Check if number n is expressed
# as sum of two abundant numbers
def SumOfAbundant(n) :
    v = ABUNDANT()
     
    for i in range(1, n + 1) :
 
        # if both i and n-i are abundant numbers
        if (list(v).count(i) and
            list(v).count(n - i)) :
            print(i, " ", n - i)
            return
             
    # can not be expressed
    print(-1)
     
# Driver code
if __name__ == "__main__" :
    n = 24
    SumOfAbundant(n)
 
# This code is contributed by Ryuga

C#




// C# program to check if number n is expressed
// as sum of two abundant numbers
using System;
using System.Collections.Generic;
 
class GFG {
 
    static readonly int N = 100005;
 
    // Function to return all abundant numbers
    // This function will be helpful for
    // multiple queries
    static HashSet<int> ABUNDANT()
    {
        // To store abundant numbers
        HashSet<int> v = new HashSet<int>();
 
        for (int i = 1; i < N; i++)
        {
 
            // to store sum of the divisors
            // include 1 in the sum
            int sum = 1;
            for (int j = 2; j * j <= i; j++)
            {
 
                // if j is proper divisor
                if (i % j == 0)
                {
                    sum += j;
 
                    // if i is not a perfect square
                    if (i / j != j)
                    {
                        sum += i / j;
                    }
                }
            }
 
            // if sum is greater than i then i is
            // a abundant number
            if (sum > i)
            {
                v.Add(i);
            }
        }
        return v;
    }
 
    // Check if number n is expressed
    // as sum of two abundant numbers
    static void SumOfAbundant(int n)
    {
        HashSet<int> v = ABUNDANT();
 
        for (int i = 1; i <= n; i++)
        {
 
            // if both i and n-i are
            // abundant numbers
            if (v.Contains(i) & v.Contains(n - i))
            {
                Console.Write(i + " " + (n - i));
                return;
            }
        }
 
        // can not be expressed
        Console.Write(-1);
    }
 
    // Driver code
    public static void Main()
    {
        int n = 24;
        SumOfAbundant(n);
    }
}
 
// This code is contributed by PrinciRaj1992

PHP




<?php
// PHP program to check if number n is
// expressed as sum of two abundant numbers
 
// Function to return all abundant numbers
// This function will be helpful for
// multiple queries
function ABUNDANT()
{
    $N = 100005;
     
    // To store abundant numbers
    $v = array();
 
    for ($i = 1; $i < $N; $i++)
    {
 
        // to store sum of the divisors
        // include 1 in the sum
        $sum = 1;
        for ($j = 2; $j * $j <= $i; $j++)
        {
 
            // if j is proper divisor
            if ($i % $j == 0)
            {
                $sum += $j;
 
                // if i is not a perfect square
                if ($i / $j != $j)
                    $sum += $i / $j;
            }
        }
 
        // if sum is greater than i then
        // i is a abundant number
        if ($sum > $i)
            array_push($v, $i);
    }
    $v = array_unique($v);
    return $v;
}
 
// Check if number n is expressed
// as sum of two abundant numbers
function SumOfAbundant($n)
{
    $v = ABUNDANT();
 
    for ($i = 1; $i <= $n; $i++)
    {
 
        // if both i and n-i are
        // abundant numbers
        if (in_array($i, $v) &&
            in_array($n - $i, $v))
        {
            echo $i, " ", $n - $i;
            return;
        }
    }
 
    // can not be expressed
    echo -1;
}
 
// Driver code
$n = 24;
SumOfAbundant($n);
 
// This code is contributed
// by Arnab Kundu
?>

Javascript




<script>
 
// javascript program to check if number n is expressed
// as sum of two abundant numbers
 
var N = 100005;
 
// Function to return all abundant numbers
// This function will be helpful for
// multiple queries
function ABUNDANT()
{
    // To store abundant numbers
    var v = new Set();
     
    var i,j;
    for (i = 1; i < N; i++) {
 
        // to store sum of the divisors
        // include 1 in the sum
        var sum = 1;
        for (j = 2; j * j <= i; j++) {
 
            // if j is proper divisor
            if (i % j == 0) {
                sum += j;
 
                // if i is not a perfect square
                if (parseInt(i / j) != j)
                    sum += parseInt(i / j);
            }
        }
 
        // if sum is greater than i then i is
        // a abundant number
        if (sum > i)
            v.add(i);
    }
 
    return v;
}
 
// Check if number n is expressed
// as sum of two abundant numbers
function SumOfAbundant(n)
{  
    var v = new Set();
    v = ABUNDANT();
    var i;
    for (i = 1; i <= n; i++) {
 
        // if both i and n-i are
        // abundant numbers
        if (v.has(i) && v.has(n - i)) {
            document.write(i+ ' ' + (n-i))
            return;
        }
    }
 
    // can not be expressed
    document.write(-1);
}
 
// Driver code
    var n = 24;
    SumOfAbundant(n);
 
</script>
Output: 
12 12

 


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