13

leet_13.py

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+# https://leetcode.com/problems/roman-to-integer/
+# Runtime: 52 ms, faster than 96.13% of Python3 online submissions for Roman to Integer.
+
+class Solution:
+    def romanToInt(self, s: str) -> int:
+        res = 0
+        values = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
+        prev = None
+        for sym in s:
+            res += values[sym]
+            if sym in ('D', 'M') and prev == 'C':
+                res -= 200
+            elif sym in ('L', 'C') and prev == 'X':
+                res -= 20
+            elif sym in ('V', 'X') and prev == 'I':
+                res -= 2
+            prev = sym
+        return res
+
+
+if __name__ == '__main__':
+    s = Solution()
+    assert s.romanToInt('III') == 3
+    assert s.romanToInt('IV') == 4
+    assert s.romanToInt('IX') == 9
+    assert s.romanToInt('LVIII') == 58
+    assert s.romanToInt('MCMXCIV') == 1994