CodingHardcod-g187

Subject Bit manipulationLevel Senior–Staff~30 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

Given a non-negative integer n (0 <= n <= 10^9), return the total number of set bits (1s) across the binary representations of every integer from 0 to n inclusive. For example for n = 5 the values 0..5 in binary contribute 0+1+1+2+1+2 = 7 set bits. An O(n) loop popcounting each number is too slow at the upper bound.

Implement

count_set_bits_upto(n: int) → int

Examples

in[5]out7

What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Learn the concepts

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.