Keep Only the Highest Set Bit

Code

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

uint16_t keep_highest_bit(uint16_t reg) {
    if (reg == 0) return 0;  // Handle zero input
        
            // Find the position of the highest set bit
                uint16_t mask = 0x8000;  // Start with MSB (bit 15)
                    
                        while (mask > 0) {
                                if (reg & mask) {
                                            return mask;  // Found the highest set bit
                                                    }
                                                            mask >>= 1;  // Check next lower bit
                                                                }
                                                                    
                                                                        return 0;  // Should not reach here for non-zero input
                                                                        }

                                                                        // Alternative more efficient version using bit scanning:
                                                                        /*
                                                                        uint16_t keep_highest_bit(uint16_t reg) {
                                                                            if (reg == 0) return 0;
                                                                                
                                                                                    // Find the position of the highest set bit
                                                                                        uint8_t pos = 15;
                                                                                            while (pos > 0) {
                                                                                                    if (reg & (1U << pos)) {
                                                                                                                break;
                                                                                                                        }
                                                                                                                                pos--;
                                                                                                                                    }
                                                                                                                                        
                                                                                                                                            return 1U << pos;
                                                                                                                                            }
                                                                                                                                            */

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

Solving Approach