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 result = reg;

    // Clear all odd bits
    result &= 0x55555555;

    result = (result | (result >> 1)) & 0x33333333;
    result = (result | (result >> 2)) & 0x0F0F0F0F;
    result = (result | (result >> 4)) & 0x00FF00FF;
    result = (result | (result >> 8)) & 0x0000FFFF;

    return result;
}

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