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

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

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

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++

 // 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[0]);        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



Output:

8

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