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 x = reg & 0x55555555u;        // keep bits at positions 0,2,4,...,30
    x = (x | (x >> 1)) & 0x33333333u;      // pack into positions 0,1,4,5,8,9,...
    x = (x | (x >> 2)) & 0x0F0F0F0Fu;      // pack further into 0..3, 8..11, ...
    x = (x | (x >> 4)) & 0x00FF00FFu;      // pack into 0..7, 16..23
    x = (x | (x >> 8)) & 0x0000FFFFu;      // final pack into 0..15
    return x;
}

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