Description

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:

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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:
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Input: num = 58

Output: "LVIII"

Explanation:

50 = L
8 = VIII

Example 3:
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Input: num = 1994

Output: "MCMXCIV"

Explanation:

1000 = M
 900 = CM
  90 = XC
   4 = IV

Constraints:

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1 <= num <= 3999

Approach

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class Solution:
    def intToRoman(self, num: int) -> str:
        if num > 3999 or num < 1:
            return ''
        
        arr = ['I','V','X','L','C','D','M']
        result = []
        value = num 
        i = 0

        while value > 0:
            d = value % 10
            value //= 10
            if d <= 3:
                result.extend([arr[i]]*d)
            elif d ==4:
                result.extend([arr[i + 1], arr[i]])
            elif d < 9:
                result.extend([arr[i]] * (d - 5))
                result.append(arr[i + 1])
            elif d == 9:
                result.extend([arr[i + 2], arr[i]])
            i += 2
        

        return ''.join(result[::-1])
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class Solution:
    def intToRoman(self, num: int) -> str:
        roman_mapping ={
            1000: "M",
            900: "CM",
            500: "D",
            400: "CD",
            100: "C",
            90: "XC",
            50: "L",
            40: "XL",
            10: "X",
            9: "IX",
            5: "V",
            4: "IV",
            1: "I"
        }

        roman_numeral = ""

        for value, symbol in roman_mapping.items():
            while num >= value:
                roman_numeral += symbol
                num -= value

        return roman_numeral