#2595 - Number of Even and Odd Bits

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Bit Manipulation

Problem Description

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

/**
 * @param {number} n
 * @return {number[]}
 */
var evenOddBit = function(n) {
  let evenCount = 0;
  let oddCount = 0;
  let index = 0;

  while (n > 0) {
    if (n & 1) {
      if (index % 2 === 0) evenCount++;
      else oddCount++;
    }
    n >>= 1;
    index++;
  }

  return [evenCount, oddCount];
};