feat(leetcode): add No.227

Author: mickey0524

227.Basic-Calculator-II.py

@@ -0,0 +1,52 @@
+# https://leetcode.com/problems/basic-calculator-ii/description/
+#
+# algorithms
+# Medium (31.8%)
+# Total Accepted:    86.8K
+# Total Submissions: 272.9K
+
+
+from collections import deque
+
+
+class Solution(object):
+    def calculate(self, s):
+        """
+        :type s: str
+        :rtype: int
+        """
+        s = s.replace(' ', '')
+        stack = deque()
+        i = 0
+        length = len(s)
+
+        while i < length:
+            if ord(s[i]) >= 48 and ord(s[i]) <= 57:
+                begin_idx = i
+                i += 1
+                while i < length and ord(s[i]) >= 48 and ord(s[i]) <= 57:
+                    i += 1
+                num = int(s[begin_idx:i])
+                if len(stack) == 0 or stack[0] == '+' or stack[0] == '-':
+                    stack.appendleft(num)
+                else:
+                    if stack[0] == '*':
+                        op = stack.popleft()
+                        another_num = stack.popleft()
+                        stack.appendleft(num * another_num)
+                    if stack[0] == '/':
+                        op = stack.popleft()
+                        another_num = stack.popleft()
+                        stack.appendleft(another_num / num)
+            else:
+                stack.appendleft(s[i])
+                i += 1
+
+        while len(stack) != 1:
+            num1 = stack.pop()
+            op = stack.pop()
+            num2 = stack.pop()
+            res = num1 + num2 if op == '+' else num1 - num2
+            stack.append(res)
+
+        return stack[0]