# Largest perfect cube number in an Array

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
```

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

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 ` `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

 ` `

Output:

```64
```

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