re-solve "224. Basic Calculator"

src/basic_calculator.py

@@ -1,30 +1,33 @@
+SIGN = {
+    "+": +1,
+    "-": -1,
+}
+
+
 class Solution:
     def calculate(self, s: str) -> int:
-        num, sign, stack = 0, 1, [0]
+        current, sign, stack = 0, +1, [0]
 
         for x in s:
-            if x.isnumeric():
-                num = num * 10 + int(x)
+            if x.isdigit():
+                current = current * 10 + int(x)
             elif x == " ":
-                continue
-            elif x == "+":
-                stack[-1] += num * sign
-                sign = 1
-                num = 0
-            elif x == "-":
-                stack[-1] += num * sign
-                sign = -1
-                num = 0
+                pass
+            elif x in SIGN:
+                stack[-1] += current * sign
+                sign = SIGN[x]
+                current = 0
             elif x == "(":
-                stack.extend([sign, 0])
+                stack.append(sign)
+                stack.append(0)
                 sign = 1
-                num = 0
+                current = 0
             elif x == ")":
-                last = (stack.pop() + num * sign) * stack.pop()
+                last = (stack.pop() + current * sign) * stack.pop()
                 stack[-1] += last
                 sign = 1
-                num = 0
+                current = 0
             else:
-                raise ValueError("unknown token: {x}")
+                raise ValueError(f"unknown token: {x}")
 
-        return stack[-1] + num * sign
+        return stack[-1] + current * sign