22. Extract Even Bits Only from 32-bit Register

#include <stdio.h>
#include <stdint.h>

uint32_t extract_even_bits(uint32_t reg) {
    // Your code here
    uint32_t mask = reg & 0x55555555;
    int count = 0;
    while(mask != 0){
        mask &= (mask-1);
        count++;
    }
    if(count){
        return (1<<count) - 1;
    }
    return 0;
}

int main() {
    uint32_t reg;
    scanf("%u", &reg);
    printf("%u", extract_even_bits(reg));
    return 0;
}