34. Count Set Bits in an 8-bit Register

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

uint8_t count_set_bits(uint8_t reg) {
    // Your code here
    reg = (reg & 0x55) + ((reg>>1) & 0x55);
    reg = (reg & 0x33) + ((reg>>2) & 0x33);
    reg = (reg & 0x0F) + ((reg>>4) & 0x0F);
    return reg;
}

int main() {
    uint8_t reg;
    scanf("%hhu", &reg);
    printf("%u", count_set_bits(reg));
    return 0;
}