I am trying to find Hamming distance between two integers, and I got it to work with:
int count = 0;
for(int i = 0; i < 32; i++)
{
if((x ^ y) & 1)
count++;
x >>= 1;
y >>= 1;
}
However, it does not work with:
if(x & 1 != y & 1)
When x = 1 and y = 4, the correct result is 2. However, the second version outputs 1. Sounds like I need a lesson in discrete logic.
How can I rewrite the second if-statement to make it work?
The != operator has a higher precedence than the & operator, so the condition as written is evaluated as x & (1 != y) & 1, but you probably want (x & 1) != (y & 1) instead.
If you want the Hamming distance, why not just use std::popcount?
#include <bit>
...
int count = std::popcount(x ^ y);
If you can't use C++20 then there is also a compiler intrinsic __builtin_popcount available for GCC and Clang, or __popcnt for MSVC:
#ifdef _MSC_VER
#include <intrin.h>
#define __builtin_popcount __popcnt
#endif
...
int count = __builtin_popcount(x ^ y);
This is because bit-wise AND has less precedence than !=
https://en.cppreference.com/w/cpp/language/operator_precedence