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

    reg = reg & 0x55555555;
    uint32_t mask = 0x1;
    int i = 0;
    uint32_t num = 0;

    while(reg)
    {
        reg = reg & reg - 1;
        i++;
    }

    reg = (1 << i) - 1;

 /*   while(i < 16)
    {
        num = ((reg & mask) >> i) | num;
        mask <<= 2;
        i++;
    }
*/
    return reg;
}

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