Add code for leetcode No.13.

Author: yanglr

Diff for: leetcode-013/leetcode013.py

@@ -0,0 +1,26 @@
+class Solution:
+    def romanToInt(self, s: str) -> int:
+        d = dict()
+        d = {
+            'I': 1,
+            'V': 5,
+            'X': 10,
+            'L': 50,
+            'C': 100,
+            'D': 500,
+            'M': 1000
+        }
+
+        sum0 = 0
+        for i in range(len(s)):
+            currentValue = d[s[i]]
+            
+            if i == len(s) -1 or d[s[i+1]] <= currentValue:  # d[s[i+1]]: nextValue
+                sum0 += d[s[i]]
+            else:
+                sum0 -= d[s[i]]
+        
+        return sum0
+
+sol = Solution()
+print(sol.romanToInt("MCMXCIV"))