Bit Reversal in an 8-bit Value

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

uint8_t reverse_bits(uint8_t val) {
    // Your logic here
    val = ((val & 0x55) << 1) | ((val & 0xAA) >> 1);
    val = ((val & 0x33) << 2) | ((val & 0xCC) >> 2);
    val = ((val & 0x0F) << 4) | ((val & 0xF0) >> 4);
    return val;
}

int main() {
    uint8_t val;
    scanf("%hhu", &val);

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

Mask based bit reversal

first it swaps the adjacent bits then swaps the adjacent pair of bits and then swaps the nibbles