0338-counting-bits.js

/**
 * 338. Counting Bits
 * https://leetcode.com/problems/counting-bits/
 * Difficulty: Easy
 *
 * Given an integer n, return an array ans of length n + 1 such that for each i (0 <= i <= n),
 * ans[i] is the number of 1's in the binary representation of i.
 */

/**
 * @param {number} n
 * @return {number[]}
 */
var countBits = function(n) {
  const result = new Array(n + 1).fill(0);
  for (let i = 0; i <= n; i++) {
    result[i] = result[i >> 1] + (i & 1);
  }
  return result;
};