[leetCode] 338. Counting Bits (Pyhton)

Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1's in their binary representation and return them as an array.

 

Example 1:

Input: 2
Output: [0,1,1]

Example 2:

Input: 5
Output: [0,1,1,2,1,2]

Follow up:

• It is very easy to come up with a solution with run time O(n*sizeof(integer)). But can you do it in linear time O(n) /possibly in a single pass?
• Space complexity should be O(n).
• Can you do it like a boss? Do it without using any builtin function like __builtin_popcount in c++ or in any other language.

Solution

class Solution:
    def countBits(self, num: int) -> List[int]:
        results = [0]
        
        for i in range(1, num+1):
            results.append(results[i & (i-1)] + 1)
            
        return results

SOMJANG/CODINGTEST_PRACTICE