338. Counting Bits
Easy
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:
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++)?