Time: 47 ms (88.57%), Space: 22.1 MB (15.75%) - LeetHub

Author: hogan-tech

0227-basic-calculator-ii/0227-basic-calculator-ii.py

@@ -0,0 +1,38 @@
+# time complexity: O(n)
+# space complexity: O(n)
+import math
+
+
+class Solution:
+    def calculate(self, s: str) -> int:
+        num = 0
+        prevOperation = '+'
+        s += '+'
+        stack = []
+        for c in s:
+            if c.isdigit():
+                num = num*10 + int(c)
+            elif c == ' ':
+                pass
+            else:
+                if prevOperation == '+':
+                    stack.append(num)
+                elif prevOperation == '-':
+                    stack.append(-num)
+                elif prevOperation == '*':
+                    operant = stack.pop()
+                    stack.append((operant*num))
+                elif prevOperation == '/':
+                    operant = stack.pop()
+                    stack.append(math.trunc(operant/num))
+                num = 0
+                prevOperation = c
+        return sum(stack)
+
+
+s = "3+2*2"
+print(Solution().calculate(s))
+s = " 3/2 "
+print(Solution().calculate(s))
+s = " 3+5 / 2 "
+print(Solution().calculate(s))