338. Counting Bits

https://leetcode.com/problems/counting-bits/

Python

• Time: O(nlogn)
• Space: O(n)

from functools import reduce


class Solution:
    def countBits(self, n: int) -> List[int]:
        return [
            reduce(lambda cur, i: cur+1 if i == '1' else cur, bin(i)[2:], 0)
            for i in range(n+1)
        ]

Javascript

var countBits = function(n) {
  const tmp = new Array(n + 1);
  return [...tmp].map((b, i) => {
    return i.toString(2).split('').reduce((acc, cur) => acc + Number(cur), 0);
  }) 
};