Compress Interleaved Bits Reverse Bit Spreading

Code

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

static inline uint8_t compress_bits(uint16_t v) {
    uint32_t x = v & 0x5555u;          // keep even positions only: 0b0101...
    x = (x | (x >> 1)) & 0x3333u;      // 0011 groups
    x = (x | (x >> 2)) & 0x0F0Fu;      // 00001111 groups
    x = (x | (x >> 4)) & 0x00FFu;      // pack into low 8
    return (uint8_t)x;
}

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

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

Solving Approach