Keep Only the Highest Set Bit

Code

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

uint16_t keep_highest_set_bit(uint16_t reg) {
    if (reg == 0) return 0;  // No bit set

    // Step 1: Propagate highest set bit downwards
    reg |= (reg >> 1);
    reg |= (reg >> 2);
    reg |= (reg >> 4);
    reg |= (reg >> 8);

    // Step 2: Keep only highest bit
    return (reg + 1) >> 1;
}

int main() {
    uint16_t reg;
    scanf("%hu", &reg);
    printf("%hu", keep_highest_set_bit(reg));
    return 0;
}

Solving Approach