338 Bits

338. Counting Bits

Medium

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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.

꼭 전단계가 아니라 i/2 경우도 생각해야한다. 이건 좀 외워야할거같다.

 

좋은 문제이자 

 

2 bits 니까

 

array를 만들고

 

저장하면 될꺼같다. 

 

i/2 + i % 2 를 더하면 된다.