405. Convert a Number to Hexadecimal – Leetcode Solutions

Example 1:

Input: num = 26
Output: "1a"

Example 2:

Input: num = -1
Output: "ffffffff"

class Solution:
    def toHex(self, num: int) -> str:
        # Handle the special case where the number is 0
        if num == 0:
            return "0"
        
        # Hexadecimal characters
        hex_chars = "0123456789abcdef"
        
        # If the number is negative, apply two's complement for 32-bit numbers
        if num < 0:
            num += 2 ** 32
        
        # Initialize an empty result string
        result = []
        
        # Extract hexadecimal digits one by one
        while num > 0:
            # Get the last 4 bits (a single hex digit)
            digit = num & 15  # Equivalent to num % 16
            result.append(hex_chars[digit])
            # Right shift the number by 4 bits
            num >>= 4
        
        # The digits are generated in reverse order, so reverse the result and join
        return ''.join(reversed(result))

class Solution {
public:
    string toHex(int num) {
        // If the number is 0, directly return "0".
        if (num == 0) return "0";

        // Array of characters to represent hexadecimal digits.
        const char hexDigits[] = "0123456789abcdef";

        // Since an integer is 32 bits, the result can have at most 8 hex digits.
        string result;

        // Loop up to 8 times (4 bits per hex digit for 32-bit numbers).
        for (int i = 0; i < 8 && num != 0; ++i) {
            // Extract the last 4 bits of the number and convert them to hex.
            result = hexDigits[num & 0xf] + result;

            // Perform a logical right shift by 4 bits.
            // For negative numbers, in two's complement representation, this will shift appropriately.
            num >>= 4;
        }

        // Return the resulting string.
        return result;
    }
};

var toHex = function(num) {
    // Handle the case when the input number is 0
    if (num === 0) {
        return "0";
    }

    // Define a map for hexadecimal characters
    // For digits 0-15, map to corresponding hexadecimal symbols
    const hexMap = "0123456789abcdef";

    // Use an unsigned 32-bit mask to handle negative numbers (two's complement)
    // If the number is negative, convert it to its 32-bit unsigned equivalent
    num = num >>> 0;

    // Initialize an empty string to store the hexadecimal result
    let hexString = "";

    // Continue dividing the number by 16 and converting the remainder
    // to the corresponding hexadecimal digit until the number becomes 0
    while (num > 0) {
        // Get the remainder when divided by 16 (the current hexadecimal digit)
        const remainder = num % 16;

        // Prepend the corresponding hex character to the result string
        hexString = hexMap[remainder] + hexString;

        // Perform integer division by 16 (shift right by 4 bits)
        num = Math.floor(num / 16);
    }

    // Return the resulting hexadecimal string
    return hexString;
};

class Solution {
    public String toHex(int num) {
        // Handle the edge case when the input number is 0
        if (num == 0) {
            return "0";
        }

        // Initialize the hexadecimal character set
        char[] hexChars = "0123456789abcdef".toCharArray();

        // The result string to hold the hexadecimal representation
        StringBuilder hexString = new StringBuilder();

        // Process each of the 8 hexadecimal digits (4 bits at a time)
        for (int i = 0; i < 8 && num != 0; i++) {
            // Extract the last 4 bits of the number
            int currentNibble = num & 0xf;

            // Convert the 4-bit value to a hexadecimal character and append it
            hexString.append(hexChars[currentNibble]);

            // Perform a logical right shift by 4 bits
            num >>>= 4;
        }

        // The StringBuilder contains the hexadecimal digits in reverse order
        // Reverse it to get the correct hexadecimal representation
        return hexString.reverse().toString();
    }
}