LeetCode 2859: Sum of Values at Indices With K Set Bits Solution

Master LeetCode problem 2859 (Sum of Values at Indices With K Set Bits), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2859. Sum of Values at Indices With K Set Bits

Easy

Array Bit Manipulation

Problem Explanation

Explanation

To solve this problem, we need to iterate through each element of the array and count the number of set bits in the binary representation of the index. If the count matches the given value k, we add the corresponding element to the result sum. We can count the number of set bits using bitwise operations.

Algorithm:

Initialize a variable sum to 0 to store the final result sum.
Iterate through each element and index of the input array nums.
For each index, count the number of set bits by using a loop that right shifts the index and checks the least significant bit.
If the count of set bits equals k, add the corresponding element to sum.
Finally, return the sum.

Time Complexity:

The time complexity of this algorithm is O(n * log(max(nums))), where n is the number of elements in the array nums and max(nums) is the maximum element in the array.

Space Complexity:

The space complexity is O(1) as we are using only a constant amount of extra space.

Solution Code

class Solution {
    public int sumOfKSetBits(int[] nums, int k) {
        int sum = 0;
        for (int i = 0; i < nums.length; i++) {
            int count = 0;
            int index = i;
            while (index > 0) {
                count += index & 1;
                index >>= 1;
            }
            if (count == k) {
                sum += nums[i];
            }
        }
        return sum;
    }
}

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