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Largest perfect cube number in an Array
  • Difficulty Level : Basic
  • Last Updated : 18 Jan, 2019

Given an array of N integers. The task is to find the largest number which is a perfect cube. Print -1 if there is no number that is perfect cube.

Examples:

Input : arr[] = {16, 8, 25, 2, 3, 10} 
Output : 25
Explanation: 25 is the largest number 
that is a perfect cube. 

Input : arr[] = {36, 64, 10, 16, 29, 25| 
Output : 64

A Simple Solution is to sort the elements and sort the N numbers and start checking from back for a perfect cube number using cbrt() function. The first number from the end which is a perfect cube number is our answer. The complexity of sorting is O(n log n) and of cbrt() function is log n, so at the worst case the complexity is O(n log n).

An Efficient Solution is to iterate for all the elements in O(n) and compare every time with the maximum element, and store the maximum of all perfect cubes.

Below is the implementation of the above approach:

C++




// CPP program to find the largest perfect
// cube number among n numbers
  
#include <bits/stdc++.h>
using namespace std;
  
// Function to check if a number
// is perfect cube number or not
bool checkPerfectcube(int n)
{
    // takes the sqrt of the number
    int d = cbrt(n);
  
    // checks if it is a perfect
    // cube number
    if (d * d * d == n)
        return true;
  
    return false;
}
  
// Function to find the largest perfect
// cube number in the array
int largestPerfectcubeNumber(int a[], int n)
{
    // stores the maximum of all
    // perfect cube numbers
    int maxi = -1;
  
    // Traverse all elements in the array
    for (int i = 0; i < n; i++) {
  
        // store the maximum if current
        // element is a perfect cube
        if (checkPerfectcube(a[i]))
            maxi = max(a[i], maxi);
    }
  
    return maxi;
}
  
// Driver Code
int main()
{
    int a[] = { 16, 64, 25, 2, 3, 10 };
  
    int n = sizeof(a) / sizeof(a[0]);
  
    cout << largestPerfectcubeNumber(a, n);
  
    return 0;
}


Java




// Java program to find the largest perfect 
// cube number among n numbers 
class Solution
{
  
// Function to check if a number 
// is perfect cube number or not 
static boolean checkPerfectcube(int n) 
    // takes the sqrt of the number 
    int d =(int) Math.cbrt(n); 
  
    // checks if it is a perfect 
    // cube number 
    if (d * d * d == n) 
        return true
  
    return false
  
// Function to find the largest perfect 
// cube number in the array 
static int largestPerfectcubeNumber(int a[], int n) 
    // stores the maximum of all 
    // perfect cube numbers 
    int maxi = -1
  
    // Traverse all elements in the array 
    for (int i = 0; i < n; i++) { 
  
        // store the maximum if current 
        // element is a perfect cube 
        if (checkPerfectcube(a[i])) 
            maxi = Math.max(a[i], maxi); 
    
  
    return maxi; 
  
// Driver Code 
public static void main(String args[])
    int a[] = { 16, 64, 25, 2, 3, 10 }; 
  
    int n =a.length; 
  
    System.out.print(largestPerfectcubeNumber(a, n)); 
  
}
  
//contributed by Arnab Kundu


Python3




# Python 3 program to find the largest 
# perfect cube number among n numbers
import math 
  
# Function to check if a number
# is perfect cube number or not
def checkPerfectcube(n):
      
    # checks if it is a perfect
    # cube number
    cube_root = n**(1./3.)
    if round(cube_root) ** 3 == n:
        return True
          
    else:
        return False
  
# Function to find the largest perfect
# cube number in the array
def largestPerfectcubeNumber(a, n):
      
    # stores the maximum of all
    # perfect cube numbers
    maxi = -1
  
    # Traverse all elements in the array
    for i in range(0, n, 1):
          
        # store the maximum if current
        # element is a perfect cube
        if (checkPerfectcube(a[i])):
            maxi = max(a[i], maxi)
  
    return maxi;
  
# Driver Code
if __name__ == '__main__':
    a = [16, 64, 25, 2, 3, 10]
  
    n = len(a)
  
    print(largestPerfectcubeNumber(a, n))
  
# This code is contributed by 
# Surendra_Gangwar


C#




//C# program to find the largest perfect 
// cube number among n numbers 
using System;
  
public class Solution
{
  
    // Function to check if a number 
    // is perfect cube number or not 
    static bool checkPerfectcube(int n) 
    
        // takes the sqrt of the number 
        int d = (int)Math.Ceiling(Math.Pow(n, (double)1 / 3));
        // checks if it is a perfect 
        // cube number 
        if (d * d * d == n) 
            return true
  
        return false
    
  
    // Function to find the largest perfect 
    // cube number in the array 
    static int largestPerfectcubeNumber(int []a, int n) 
    
        // stores the maximum of all 
        // perfect cube numbers 
        int maxi = -1; 
  
        // Traverse all elements in the array 
        for (int i = 0; i < n; i++) { 
  
            // store the maximum if current 
            // element is a perfect cube 
            if (checkPerfectcube(a[i])) 
                maxi = Math.Max(a[i], maxi); 
        
  
        return maxi; 
    
  
    // Driver Code 
    public static void Main()
    
        int []a = { 16, 64, 25, 2, 3, 10 }; 
  
        int n =a.Length; 
  
        Console.WriteLine(largestPerfectcubeNumber(a, n)); 
  
    
}
  
/*This code is contributed by PrinciRaj1992*/


PHP




<?php 
// PHP program to find the largest perfect
// cube number among n numbers
  
// Function to check if a number
// is perfect cube number or not
function checkPerfectcube($n)
{
    // takes the sqrt of the number
    $d = pow($n, (1 / 3));
    $d = round($d);
  
    // checks if it is a perfect
    // cube number
    if ($d * $d * $d == $n)
        return true;
  
    return false;
}
  
// Function to find the largest perfect
// cube number in the array
function largestPerfectcubeNumber(&$a, $n)
{
    // stores the maximum of all
    // perfect cube numbers
    $maxi = -1;
  
    // Traverse all elements in the array
    for ($i = 0; $i < $n; $i++)
    {
  
        // store the maximum if current
        // element is a perfect cube
        if (checkPerfectcube($a[$i]))
            $maxi = max($a[$i], $maxi);
    }
  
    return $maxi;
}
  
// Driver Code
$a = array( 16, 64, 25, 2, 3, 10 );
$n = sizeof($a);
echo largestPerfectcubeNumber($a, $n);
  
// This code is contributed by ita_c
?>


Output:

64

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