Compress Interleaved Bits Reverse Bit Spreading

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

uint8_t compress_bits(uint16_t val) {
    uint8_t reg=0, res;
    for(int i=0; i<16; i++) {
        if(i%2==0) {
            reg <<= 1;
            reg |= (val & 1);
        }
        val >>= 1;    
    }
    for(int i=0; i<8; i++) {
        res <<=1;
        res |= (reg & 1);
        reg >>=1;

    }
    return res;
}

int main() {
    uint16_t val;
    scanf("%hu", &val);

    uint8_t result = compress_bits(val);
    printf("%u", result);
    return 0;
}