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
    uint32_t mask = 0x55555555;
    uint32_t even = reg & mask;

    // Pack even bits by discarding zeros (right shift progressively)
    uint32_t packed = 0;
    int pos = 0;

    for (int i = 0; i < 32; i += 2) {
        if (even & (1U << i)) {
            packed |= (1U << pos);
        }
        pos++;
    }

    return packed;
        
}

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