22. Extract Even Bits Only from 32-bit Register

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

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