Largest number in an array that is not a perfect cube

Given an array of n integers. The task is to find the largest number which is not a perfect cube. Print -1 if there is no number that is a perfect cube.

Examples:

Input: arr[] = {16, 8, 25, 2, 3, 10} 
Output: 25
25 is the largest number that is not a perfect cube. 

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

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

A Simple Solution is to sort the elements and sort then numbers and start checking from back for a non-perfect cube number using cbrt() function. The first number from the end which is not 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 non-perfect cubes.

Below is the implementation of the above approach:

C++

// CPP program to find the largest non-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 non perfect 
// cube number in the array 
int largestNonPerfectcubeNumber(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 non 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 << largestNonPerfectcubeNumber(a, n); 
  
    return 0; 
} 

Java

// Java program to find the largest non-perfect 
// cube number among n numbers 
  
import java.io.*; 
  
class GFG { 
    
  
// 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 non perfect 
// cube number in the array 
static int largestNonPerfectcubeNumber(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 non 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( largestNonPerfectcubeNumber(a, n)); 
    } 
} 
// This code is contributed  
// by inder_verma 

Python 3

# Python 3 program to find the largest  
# non-perfect cube number among n numbers 
import math 
  
# Function to check if a number 
# is perfect cube number or not 
def checkPerfectcube(n): 
      
    # takes the sqrt of the number 
    cube_root = n ** (1./3.) 
    if round(cube_root) ** 3 == n: 
        return True
    else: 
        return False
  
# Function to find the largest non  
# perfect cube number in the array 
def largestNonPerfectcubeNumber(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 non perfect cube 
        if (checkPerfectcube(a[i]) == False): 
            maxi = max(a[i], maxi) 
      
    return maxi 
  
# Driver Code 
if __name__ == '__main__': 
    a = [16, 64, 25, 2, 3, 10]  
  
    n = len(a) 
  
    print(largestNonPerfectcubeNumber(a, n)) 
  
# This code is contributed by  
# Surendra_Gangwar 

C#

// C# program to find the largest non-perfect 
// cube number among n numbers 
using System; 
public class GFG { 
  
  
    // 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 non perfect 
    // cube number in the array 
    static int largestNonPerfectcubeNumber(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 non perfect cube 
            if (checkPerfectcube(a[i])==false) 
                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( largestNonPerfectcubeNumber(a, n)); 
        } 
} 
/*This code is contributed by PrinciRaj1992*/

PHP

<?php 
// PHP program to find the largest non-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 
    $d = (int)round(pow($n, 1/3)); 
    // checks if it is a perfect 
    // cube number 
    if ($d * $d * $d == $n) 
        return true; 
  
    return false; 
} 
  
// Function to find the largest non perfect 
// cube number in the array 
function largestNonPerfectcubeNumber($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 non perfect cube 
        if (!checkPerfectcube($a[$i])) 
            $maxi = max($a[$i], $maxi); 
    } 
  
    return $maxi; 
} 
  
// Driver Code 
  
    $a = array( 16, 64, 25, 2, 3, 10 ); 
  
    $n = count($a); 
  
    echo largestNonPerfectcubeNumber($a, $n); 
  
  
// this code is contributed by mits 
?> 

Output:

Time Complexity : O(n)

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python 3

C#

PHP

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