countingBits.js

////////////////////////////////////////////////Counting Bits///////////////////////////////////////////
// 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.
// Example 1:
// Input: n = 2
// Output: [0,1,1]
// Explanation:
// 0 --> 0
// 1 --> 1
// 2 --> 10
// Example 2:
// Input: n = 5
// Output: [0,1,1,2,1,2]
// Explanation:
// 0 --> 0
// 1 --> 1
// 2 --> 10
// 3 --> 11
// 4 --> 100
// 5 --> 101
// Constraints:
// 0 <= n <= 105
// Follow up:
// It is very easy to come up with a solution with a runtime of O(n log n). Can you do it in linear time O(n) and possibly in a single pass?
// Can you do it without using any built-in function (i.e., like __builtin_popcount in C++)?
/**
 * @param {number} n
 * @return {number[]}
 */
 const countBits = function(n) {
    let res = [];
    for (let i = 0; i <= n; i++)
        // remove 0 from bits
        res.push(Number(i).toString(2).replace(/0/g, '').length);
    return res;
};

// console.log(countBits(2));
// console.log(countBits(5));