CountingBits.py

"""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 """
from typing import List

class Solution:
    def countBits(self, n: int) -> List[int]:
        dp=[0] * (n+1)
        for n in range(1, len(dp)):
            dp[n] = dp[n//2] + n % 2 #same number of bits if it is a double of a number, otherwise +1
        return dp