Introduction

In this blog post, we will explore how to solve the LeetCode problem "12" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

Seven different symbols represent Roman numerals with the following values: Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 Roman numerals are formed by appending the conversions of decimal place values from highest to lowest. Converting a decimal place value into a Roman numeral has the following rules: If the value does not start with 4 or 9, select the symbol of the maximal value that can be subtracted from the input, append that symbol to the result, subtract its value, and convert the remainder to a Roman numeral. If the value starts with 4 or 9 use the subtractive form representing one symbol subtracted from the following symbol, for example, 4 is 1 (I) less than 5 (V): IV and 9 is 1 (I) less than 10 (X): IX. Only the following subtractive forms are used: 4 (IV), 9 (IX), 40 (XL), 90 (XC), 400 (CD) and 900 (CM). Only powers of 10 (I, X, C, M) can be appended consecutively at most 3 times to represent multiples of 10. You cannot append 5 (V), 50 (L), or 500 (D) multiple times. If you need to append a symbol 4 times use the subtractive form. Given an integer, convert it to a Roman numeral. Example 1: Input: num = 3749 Output: "MMMDCCXLIX" Explanation: 3000 = MMM as 1000 (M) + 1000 (M) + 1000 (M) 700 = DCC as 500 (D) + 100 (C) + 100 (C) 40 = XL as 10 (X) less of 50 (L) 9 = IX as 1 (I) less of 10 (X) Note: 49 is not 1 (I) less of 50 (L) because the conversion is based on decimal places Example 2: Input: num = 58 Output: "LVIII" Explanation: 50 = L 8 = VIII Example 3: Input: num = 1994 Output: "MCMXCIV" Explanation: 1000 = M 900 = CM 90 = XC 4 = IV Constraints: 1 <= num <= 3999

Explanation

• Value Mapping: Create a mapping of Roman numerals to their integer values, including subtractive pairs (e.g., "CM", "CD", etc.). This allows efficient lookup and construction of the Roman numeral string.
  • Greedy Conversion: Iterate through the value mapping in descending order. For each numeral, check how many times its value can be subtracted from the input number. Append the numeral to the result string and reduce the input number accordingly.

• Runtime Complexity: O(1) & Storage Complexity: O(1) (Since the input range is limited to 1-3999, the number of operations and the size of the lookup table are constant.)

Code

    def intToRoman(num: int) -> str:
    """
    Converts an integer to a Roman numeral.

    Args:
        num: The integer to convert (1 <= num <= 3999).

    Returns:
        The Roman numeral representation of the integer.
    """

    roman_map = { 1: 'I', 4: 'IV', 5: 'V', 9: 'IX', 10: 'X', 40: 'XL', 50: 'L', 90: 'XC', 100: 'C', 400: 'CD', 500: 'D', 900: 'CM', 1000: 'M'}

    result = ""

    values = list(roman_map.keys())
    values.sort(reverse=True)

    i = 0
    while num > 0:
        if values[i] <= num:
            result += roman_map[values[i]]
            num -= values[i]
        else:
            i += 1

    return result