added calculateII.py Basic Calculator II

0ff5ec · 0ff5ec · commit 1c2522449834 · 2018-04-06T15:01:13.000-07:00
diff --git a/calculateII.py b/calculateII.py
@@ -0,0 +1,36 @@
+#    -*-    coding: utf-8    -*-
+'''
+Implement a basic calculator to evaluate a simple expression string.
+
+The expression string contains only non-negative integers, +, -, *, / operators and empty spaces . The integer division should truncate toward zero.
+
+You may assume that the given expression is always valid.
+
+Some examples:
+"3+2*2" = 7
+" 3/2 " = 1
+" 3+5 / 2 " = 5
+Note: Do not use the eval built-in library function.
+'''
+"""
+        :type s: str
+        :rtype: int
+        """
+class Solution:
+    def calculate(self, s):
+        opList, x, operator = [], 0, None
+        for i in (s + '+'):
+            if ord('0') - 1 < ord(i) < ord('9') + 1: 
+                x = x * 10 + ord(i) - ord('0')
+            elif i != ' ':
+                if operator == '-': x *= -1
+                elif operator == '*': x *= opList.pop()
+                elif operator == '/': x = int(opList.pop() * 1.0 / x)
+                operator = i
+                opList.append(x)
+                x = 0
+        return sum(opList)
+
+if __name__ == "__main__":
+	sol = Solution()
+	print(sol.calculate(raw_input('Enter the expression: ')))
