cpp-flashcards/org/study_deck_02/dsa/bit-manipulation/0338-counting-bits.org

• 0338. Counting Bits
  • Approach
  • Python
  • C++

TODO 0338. 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:

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

Constraints:

• 0 <= n <= 10^{5}

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++)?

TODO Approach

Write your approach here.

TODO Python

class Solution:
    def countBits(self, n: int) -> List[int]:

TODO C++

class Solution {
public:
    vector<int> countBits(int n) {
        
    }
};