Number of even and odd bits

Bit Manipulation

73.4% acceptance

Feb 25, 2026

371

117

You are given a positive integer n. Let even denote the number of even indices in the binary representation of n with value 1. Let odd denote the number of odd indices in the binary representation of n with value 1. Note that bits are indexed from right to left in the binary representation of a number. Return the array [even, odd].

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn even_odd_bit(n: i32) -> Vec<i32> {
    // Count bits set at even indices (0,2,4,...) and odd indices (1,3,5,...).
    let mut even = 0;
    let mut odd = 0;
    let mut x = n;
    let mut idx = 0;
    while x > 0 {
      if x & 1 == 1 {
        if idx % 2 == 0 { even += 1; } else { odd += 1; }
      }
      x >>= 1;
      idx += 1;
    }
    vec![even, odd]
  }
}