Numbers less than N that are perfect cubes and the sum of their digits reduced to a single digit is 1

Given a number n, the task is to print all the numbers less than or equal to n which are perfect cubes as well as the eventual sum of their digits is 1.

Examples:

Input: n = 100
Output: 1 64
64 = 6 + 4 = 10 = 1 + 0 = 1
Input: n = 1000
Output: 1 64 343 1000

Approach: For every perfect cube less than or equal to n keep on calculating the sum of its digits until the number is reduced to a single digit ( O(1) approach here ), if this digit is 1 then print the perfect cube else skip to the next perfect cube below n until all the perfect cubes have been considered.

Below is the implementation of the above approach:

C++

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// C++ implementation of the approach
#include <cmath>
#include <iostream>
using namespace std;
  
// Functin that returns true if the eventual
// digit sum of number nm is 1
bool isDigitSumOne(int nm)
{
   //if reminder will 1 
   //then eventual sum is 1
    if (nm % 9 == 1)
        return true;
    else
        return false;
}
  
// Function to print the required numbers
// less than n
void printValidNums(int n)
{
    int cbrt_n = (int)cbrt(n);
    for (int i = 1; i <= cbrt_n; i++) {
        int cube = pow(i, 3);
  
        // If it is the required perfect cube
        if (cube >= 1 && cube <= n && isDigitSumOne(cube))
            cout << cube << " ";
    }
}
  
// Driver code
int main()
{
    int n = 1000;
    printValidNums(n);
    return 0;
}

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Java

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// Java implementation of the approach
class GFG {
  
    // Functin that returns true if the eventual
    // digit sum of number nm is 1
    static boolean isDigitSumOne(int nm)
    {
  
      //if reminder will 1 
      //then eventual sum is 1
      if (nm % 9 == 1)
        return true;
      else
        return false;
    }
  
    // Function to print the required numbers
    // less than n
    static void printValidNums(int n)
    {
        int cbrt_n = (int)Math.cbrt(n);
        for (int i = 1; i <= cbrt_n; i++) {
            int cube = (int)Math.pow(i, 3);
  
            // If it is the required perfect cube
            if (cube >= 1 && cube <= n && isDigitSumOne(cube))
                System.out.print(cube + " ");
        }
    }
  
    // Driver code
    public static void main(String args[])
    {
        int n = 1000;
        printValidNums(n);
    }
}

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Python

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# Python3 implementation of the approach
import math
  
# Functin that returns true if the eventual 
# digit sum of number nm is 1
def isDigitSumOne(nm) :
   #if reminder will 1 
   #then eventual sum is 1
    if(nm % 9 == 1):
        return True
    else:
        return False
  
# Function to print the required numbers
# less than n
def printValidNums(n):
    cbrt_n = math.ceil(n**(1./3.))
    for i in range(1, cbrt_n + 1):
        cube = i * i * i
        if (cube >= 1 and cube <= n and isDigitSumOne(cube)):
            print(cube, end = " ")
              
  
# Driver code 
n = 1000
printValidNums(n)

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C#

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// C# implementation of the approach
using System;
  
class GFG
{
    // Functin that returns true if the
    // eventual digit sum of number nm is 1
    static bool isDigitSumOne(int nm)
    {
  
     //if reminder will 1 
     //then eventual sum is 1
      if (nm % 9 == 1)
         return true;
      else
         return false;
    }
  
    // Function to print the required 
    // numbers less than n
    static void printValidNums(int n)
    {
        int cbrt_n = (int)Math.Ceiling(Math.Pow(n, 
                                      (double) 1 / 3));
        for (int i = 1; i <= cbrt_n; i++) 
        {
            int cube = (int)Math.Pow(i, 3);
  
            // If it is the required perfect cube
            if (cube >= 1 && cube <= n && 
                             isDigitSumOne(cube))
                Console.Write(cube + " ");
        }
    }
  
    // Driver code
    static public void Main ()
    {
        int n = 1000;
        printValidNums(n);
    }
}
  
// This code is contributed by akt_mit 

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PHP

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<?php
// PHP implementation of the approach 
  
// Functin that returns true if the 
// eventual digit sum of number nm is 1 
function isDigitSumOne($nm
     //if reminder will 1 
    //then eventual sum is 1
    if ($nm % 9 == 1) 
        return true; 
    else
        return false; 
  
// Function to print the required numbers 
// less than n 
function printValidNums($n
    $cbrt_n = ceil(pow($n,1/3)); 
    for ($i = 1; $i <= $cbrt_n; $i++) 
    
        $cube = pow($i, 3); 
  
        // If it is the required perfect cube 
        if ($cube >= 1 && $cube <= $n && 
                    isDigitSumOne($cube)) 
            echo $cube, " "
    
  
// Driver code 
$n = 1000; 
printValidNums($n); 
  
// This code is contributed by Ryuga
?>

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Output:

1 64 343 1000


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