Related Articles

# Smallest power of 2 which is greater than or equal to sum of array elements

• Difficulty Level : Basic
• Last Updated : 07 Apr, 2021

Given an array of N numbers where values of the array represent memory sizes. The memory that is required by the system can only be represented in powers of 2. The task is to return the size of the memory required by the system.
Examples:

```Input: a[] = {2, 1, 4, 5}
Output: 16
The sum of memory required is 12,
hence the nearest power of 2 is 16.

Input: a[] = {1, 2, 3, 2}
Output: 8```

Source: Microsoft Interview

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

Approach: The problem is a combination of summation of array elements and smallest power of 2 greater than or equal to N. Find the sum of array elements and then find the smallest power of 2 greater than or equal to N.
Below is the implementation of the above approach:

## C++

 `// C++ implementation of the above approach``#include ``using` `namespace` `std;` `// Function to find the nearest power of 2``int` `nextPowerOf2(``int` `n)``{` `    ``// The number``    ``int` `p = 1;` `    ``// If already a power of 2``    ``if` `(n && !(n & (n - 1)))``        ``return` `n;` `    ``// Find the next power of 2``    ``while` `(p < n)``        ``p <<= 1;` `    ``return` `p;``}` `// Function to find the memory used``int` `memoryUsed(``int` `arr[], ``int` `n)``{``    ``// Sum of array``    ``int` `sum = 0;` `    ``// Traverse and find the sum of array``    ``for` `(``int` `i = 0; i < n; i++)``        ``sum += arr[i];` `    ``// Function call to find the nearest power of 2``    ``int` `nearest = nextPowerOf2(sum);` `    ``return` `nearest;``}``// Driver Code``int` `main()``{``    ``int` `arr[] = { 1, 2, 3, 2 };``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);` `    ``cout << memoryUsed(arr, n);` `    ``// getchar();``    ``return` `0;``}`

## Java

 `// Java implementation of the above approach` `class` `GFG``{``    ``// Function to find the nearest power of 2``    ``static` `int` `nextPowerOf2(``int` `n)``    ``{``    ` `        ``// The number``        ``int` `p = ``1``;``    ` `        ``// If already a power of 2``        ``if``(n!=``0` `&& ((n&(n-``1``)) == ``0``))``            ``return` `n;``    ` `        ``// Find the next power of 2``        ``while` `(p < n)``            ``p <<= ``1``;``    ` `        ``return` `p;``    ``}``    ` `    ``// Function to find the memory used``    ``static` `int` `memoryUsed(``int` `arr[], ``int` `n)``    ``{``        ``// Sum of array``        ``int` `sum = ``0``;``    ` `        ``// Traverse and find the sum of array``        ``for` `(``int` `i = ``0``; i < n; i++)``            ``sum += arr[i];``    ` `        ``// Function call to find the nearest power of 2``        ``int` `nearest = nextPowerOf2(sum);``    ` `        ``return` `nearest;``    ``}``    ``// Driver Code``    ``public` `static` `void` `main(String []args)``    ``{``        ``int` `arr[] = { ``1``, ``2``, ``3``, ``2` `};``        ``int` `n = arr.length;``    ` `        ``System.out.println(memoryUsed(arr, n));``    `  `    ``}``}` `// This code is contributed``// by ihritik`

## Python3

 `# Python3 implementation of the above approach` `# Function to find the nearest power of 2``def` `nextPowerOf2(n):``    ` `    ``# The number``    ``p ``=` `1``    ` `    ``# If already a power of 2``    ``if` `(n ``and` `not``(n & (n ``-` `1``))):``        ``return` `n``        ` `    ``# Find the next power of 2``    ``while` `(p < n):``        ``p <<``=` `1``    ``return` `p` `# Function to find the memory used``def` `memoryUsed(arr, n):``    ` `    ``# Sum of array``    ``sum` `=` `0` `    ``# Traverse and find the sum of array``    ``for` `i ``in` `range``(n):``        ``sum` `+``=` `arr[i]` `    ``# Function call to find the nearest``    ``# power of 2``    ``nearest ``=` `nextPowerOf2(``sum``)` `    ``return` `nearest` `# Driver Code``arr ``=` `[``1``, ``2``, ``3``, ``2``]``n ``=` `len``(arr)``print``(memoryUsed(arr, n))` `# This code is contributed by sahishelangia`

## C#

 `// C# implementation of the above approach` `using` `System;``class` `GFG``{``    ``// Function to find the nearest power of 2``    ``static` `int` `nextPowerOf2(``int` `n)``    ``{``    ` `        ``// The number``        ``int` `p = 1;``    ` `        ``// If already a power of 2``        ``if``(n!=0 && ((n&(n-1)) == 0))``            ``return` `n;``    ` `        ``// Find the next power of 2``        ``while` `(p < n)``            ``p <<= 1;``    ` `        ``return` `p;``    ``}``    ` `    ``// Function to find the memory used``    ``static` `int` `memoryUsed(``int` `[]arr, ``int` `n)``    ``{``        ``// Sum of array``        ``int` `sum = 0;``    ` `        ``// Traverse and find the sum of array``        ``for` `(``int` `i = 0; i < n; i++)``            ``sum += arr[i];``    ` `        ``// Function call to find the nearest power of 2``        ``int` `nearest = nextPowerOf2(sum);``    ` `        ``return` `nearest;``    ``}``    ``// Driver Code``    ``public` `static` `void` `Main()``    ``{``        ``int` `[]arr = { 1, 2, 3, 2 };``        ``int` `n = arr.Length;``    ` `        ``Console.WriteLine(memoryUsed(arr, n));``    `  `    ``}``}` `// This code is contributed``// by ihritik`

## PHP

 ``

## Javascript

 ``
Output:
`8`

My Personal Notes arrow_drop_up