# 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 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



Output:

25

Time Complexity : O(n)

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