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Convert a Number to Hexadecimal

Difficulty: Easy

Problem Description

Given a 32-bit integer num, return a string representing its hexadecimal representation. For negative integers, two’s complement method is used. All letters in the answer string should be lowercase characters, and there should not be any leading zeros in the answer except for the zero itself.

Key Insights

  • Hexadecimal representation uses base 16, which includes digits 0-9 and letters a-f.
  • The two's complement representation for negative integers allows us to convert them into a positive equivalent for hexadecimal conversion.
  • The process of conversion involves repeatedly dividing the number by 16 and using the remainder to determine the corresponding hexadecimal digit.

Space and Time Complexity

Time Complexity: O(log n) - The number of digits in the hexadecimal representation grows logarithmically with the size of the number. Space Complexity: O(1) - We are using a fixed amount of space for variables, regardless of the input size.

Solution

To convert a number to its hexadecimal representation, we can use a loop to divide the number by 16 and keep track of the remainders. The remainders correspond to the hexadecimal digits, which can be stored in a string. For negative numbers, we convert them to their two's complement form before processing.

Code Solutions

def toHex(num):
    if num == 0:
        return "0"
    
    hex_chars = "0123456789abcdef"
    result = []
    
    for _ in range(8):  # A 32-bit integer has at most 8 hex digits
        hex_digit = num & 0xF  # Get the last 4 bits
        result.append(hex_chars[hex_digit])  # Append the corresponding hex character
        num >>= 4  # Right shift by 4 bits to process the next digit
        if num == 0:  # Stop if there are no more digits
            break
    
    return ''.join(reversed(result))  # Reverse the result for the correct order
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