Programming Technical Interview Questions
This site features a collection of common technical interview questions gathered by a group of programmers who have been through, and given, lots of technical interviews. There is an emphasis on C++ and game programming technical interviews, but most of the questions are relevant to any technical interview.
Bits ‘n Bytes
C/C++ Interview Questions, Optimization Questions

Write a function that returns the number of bits that are “on” (set to 1) in a byte. How can you make this function as fast as possible?

int countBits(unsigned char aByte)
{

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The idea is to bit-and with n-1. Every time this is done, the ’1′ on the LSB becomes 0.
Do this till the whole number becomes 0.

int count = 0;
while (n) { n = n&(n-1); count ++ }

return count;

By Nix on 09.29.09 1:23 pm | Permalink

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