Sum of Values at Indices With K Set Bits

Problem Description

You are given a 0-indexed integer array nums and an integer k. Return an integer that denotes the sum of elements in nums whose corresponding indices have exactly k set bits in their binary representation. The set bits in an integer are the 1's present when it is written in binary.

Key Insights

• Each index of the array can be represented in binary.
• The task is to count the number of 1 bits (set bits) in the binary representation of each index.
• If the count of set bits equals k, we include the corresponding element from nums in the sum.
• Efficiently calculating the number of set bits can be achieved using bit manipulation techniques.

Space and Time Complexity

Time Complexity: O(n * log(m)), where n is the length of the nums array and m is the maximum index which is at most n-1 (the bit length of n). Space Complexity: O(1), as we are using a constant amount of space.

Solution

To solve the problem, we will iterate through each index of the nums array and calculate the number of set bits for that index using a bit manipulation technique. If the number of set bits equals k, we will add the corresponding value from nums to a sum accumulator.

• We will use a loop to go through all indices from 0 to len(nums) - 1.
• For each index, we will count the set bits and check if it equals k.
• Finally, return the accumulated sum.

Code Solutions