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Largest number in an array that is not a perfect cube
• Difficulty Level : Basic
• Last Updated : 22 Feb, 2021

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```

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 ``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);` `    ``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

 ``
Output:
`25`

Time Complexity : O(n)

Auxiliary Space: O(1)

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