Keep Only the Highest Set Bit

Code

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

#define BIT_SHIFT(n)  (1 << n)

// Complete the function
uint16_t highest_set_bit(uint16_t reg) {
    if (reg == 0){ 
        return 0;
    }
    int last_index = 0; 
    // loop through all, save index where the last 1 was seen before hitting 0 
    for (int i = 0; i < 16; i++){ 
        if (reg & BIT_SHIFT(i)) { 
            last_index = i; 
            reg &= ~(BIT_SHIFT(i)); 
        }
    }
    // printf("%d \n" , last_index); 
    reg |= BIT_SHIFT(last_index);
    
    return reg;
}

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

    uint16_t result = highest_set_bit(reg);
    printf("%hu", result);
    return 0;
}

Solving Approach