LeetCode — Roman to Integer

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

Symbol       Value
I 1
V 5
X 10
L 50
C 100
D 500
M 1000
  • X can be placed before L (50) and C (100) to make 40 and 90.
  • C can be placed before D (500) and M (1000) to make 400 and 900.
Input: s = "III"
Output: 3
Input: s = "IV"
Output: 4
Input: s = "IX"
Output: 9
Input: s = "LVIII"
Output: 58
Explanation: L = 50, V= 5, III = 3.
Input: s = "MCMXCIV"
Output: 1994
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
  • s contains only the characters ('I', 'V', 'X', 'L', 'C', 'D', 'M').
  • It is guaranteed that s is a valid roman numeral in the range [1, 3999].

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