22. Extract Even Bits Only from 32-bit Register

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

uint32_t extract_even_bits(uint32_t reg) {
    int mask = (1 << 16) - 1;
    for (int i = 2,j = 1; i < 32; i += 2, j++) {
        reg &= ~(1 << j);
        reg |= ((reg & (1 << i)) >> i) << j;
    }
    return reg & mask;
}

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