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 = 1;
    uint32_t retval = 0;
    for(uint32_t i =0; i<16; ++i)
    {
        retval |= (((reg & mask)>>i*2)<<i);
        mask <<= 2;
    }
    return retval;
}

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