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 &= 0x55555555u;
    reg = (reg | (reg >> 1))  & 0x33333333; // compress pairs
    reg = (reg | (reg >> 2))  & 0x0F0F0F0F; // compress nibbles
    reg = (reg | (reg >> 4))  & 0x00FF00FF; // compress bytes
    reg = (reg | (reg >> 8))  & 0x0000FFFF; // compress to 16 bits

    return reg;
}

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