22. Extract Even Bits Only from 32-bit Register

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

uint32_t extract_even_bits(uint32_t reg) {
    uint32_t x = reg & 0x55555555;

    x = (x | (x >> 1)) & 0x33333333;
    x = (x | (x >> 2)) & 0x0f0f0f0f;
    x = (x | (x >> 4)) & 0x00ff00ff;
    x = (x | (x >> 8)) & 0x0000FFFF;
    return (uint16_t) x;
}

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