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 &= 0x55555555;                        // keep even bits
    reg = (reg | (reg >> 1)) & 0x33333333;
    reg = (reg | (reg >> 2)) & 0x0F0F0F0F;
    reg = (reg | (reg >> 4)) & 0x00FF00FF;
    reg = (reg | (reg >> 8)) & 0x0000FFFF;
    return reg;
}

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