Given a string roman_numeral consisting of characters I, V, X, L, C, D, and M, representing a valid Roman numeral in the range [1, 3999], return its integer value. Roman numerals are written according to standard rules, including subtractive notation (e.g., IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900).
Example 1
Input: roman_numeral=XCIII
Output: 93
Explanation: XC = 90, III = 3, so 90 + 3 = 93.
Example 2
Input: roman_numeral=CDXLIV
Output: 444
Explanation: CD = 400, XL = 40, IV = 4, so 400 + 40 + 4 = 444.
Example 3
Input: roman_numeral=MMXXI
Output: 2021
Explanation: MM = 2000, XXI = 21, so 2000 + 21 = 2021.
Constraints
Case 1
Input: roman_numeral='DCCCXC'
Expected: 890
Case 2
Input: roman_numeral='LXXVII'
Expected: 77
Case 3
Input: roman_numeral='MMDCCCLXXXVIII'
Expected: 2888
Case 4
Input: roman_numeral='CXXIV'
Expected: 124
Case 5
Input: roman_numeral='IX'
Expected: 9