11. 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


class Solution:
    def countBits(self, n: int) -> List[int]:
        dp = [0] * (n+1)
        offset = 1
        for i in range(1,n+1):
            if offset * 2 == i:
                offset = i
            dp[i] = 1 + dp[i-offset]
        return dp