Sum of values at indices with k set bits

Array Bit Manipulation

86.1% acceptance

Feb 25, 2026

317

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. For example, the binary representation of 21 is 10101, which has 3 set bits.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn sum_indices_with_k_set_bits(nums: Vec<i32>, k: i32) -> i32 {
    nums.iter().enumerate()
      .filter(|&(i, _)| (i as i32).count_ones() as i32 == k)
      .map(|(_, &v)| v)
      .sum()
  }
}