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feat: add Basic Calculator
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‎.templates/leetcode/json/basic_calculator.json‎

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{
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"problem_name": "basic_calculator",
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"solution_class_name": "Solution",
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"problem_number": "224",
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"problem_title": "Basic Calculator",
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"difficulty": "Hard",
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"topics": "Math, String, Stack, Recursion",
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"tags": ["grind-75"],
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"readme_description": "Given a string `s` representing a valid expression, implement a basic calculator to evaluate it, and return the result of the evaluation.\n\n**Note:** You are **not** allowed to use any built-in function which evaluates strings as mathematical expressions, such as `eval()`.",
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"readme_examples": [
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{ "content": "```\nInput: s = \"1 + 1\"\nOutput: 2\n```" },
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{ "content": "```\nInput: s = \" 2-1 + 2 \"\nOutput: 3\n```" },
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{ "content": "```\nInput: s = \"(1+(4+5+2)-3)+(6+8)\"\nOutput: 23\n```" }
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],
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"readme_constraints": "- `1 <= s.length <= 3 * 10^5`\n- `s` consists of digits, `'+'`, `'-'`, `'('`, `')'`, and `' '`.\n- `s` represents a valid expression.\n- `'+'` is **not** used as a unary operation (i.e., `\"+1\"` and `\"+(2 + 3)\"` is invalid).\n- `'-'` could be used as a unary operation (i.e., `\"-1\"` and `\"-(2 + 3)\"` is valid).\n- There will be no two consecutive operators in the input.\n- Every number and running calculation will fit in a signed 32-bit integer.",
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"readme_additional": "",
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"solution_imports": "",
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"solution_methods": [
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{ "name": "calculate", "parameters": "s: str", "return_type": "int", "dummy_return": "0" }
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],
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"test_imports": "import pytest\nfrom leetcode_py.test_utils import logged_test\nfrom .solution import Solution",
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"test_class_name": "BasicCalculator",
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"test_helper_methods": [
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{ "name": "setup_method", "parameters": "", "body": "self.solution = Solution()" }
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],
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"test_methods": [
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{
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"name": "test_calculate",
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"parametrize": "s, expected",
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"parametrize_typed": "s: str, expected: int",
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"test_cases": "[(\"1 + 1\", 2), (\" 2-1 + 2 \", 3), (\"(1+(4+5+2)-3)+(6+8)\", 23), (\"1\", 1), (\"-1\", -1), (\"-(1+2)\", -3), (\"2147483647\", 2147483647), (\"1-1+1\", 1)]",
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"body": "result = self.solution.calculate(s)\nassert result == expected"
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}
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],
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"playground_imports": "from solution import Solution",
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"playground_test_case": "# Example test case\ns = '(1+(4+5+2)-3)+(6+8)'\nexpected = 23",
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"playground_execution": "result = Solution().calculate(s)\nresult",
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"playground_assertion": "assert result == expected"
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}

‎Makefile‎

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PYTHON_VERSION = 3.13
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PROBLEM ?= find_median_from_data_stream
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PROBLEM ?= basic_calculator
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FORCE ?= 0
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COMMA := ,
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‎leetcode/basic_calculator/README.md‎

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# Basic Calculator
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**Difficulty:** Hard
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**Topics:** Math, String, Stack, Recursion
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**Tags:** grind-75
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**LeetCode:** [Problem 224](https://leetcode.com/problems/basic-calculator/description/)
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## Problem Description
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Given a string `s` representing a valid expression, implement a basic calculator to evaluate it, and return the result of the evaluation.
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**Note:** You are **not** allowed to use any built-in function which evaluates strings as mathematical expressions, such as `eval()`.
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## Examples
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### Example 1:
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```
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Input: s = "1 + 1"
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Output: 2
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```
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### Example 2:
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```
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Input: s = " 2-1 + 2 "
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Output: 3
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```
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### Example 3:
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```
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Input: s = "(1+(4+5+2)-3)+(6+8)"
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Output: 23
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```
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## Constraints
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- `1 <= s.length <= 3 * 10^5`
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- `s` consists of digits, `'+'`, `'-'`, `'('`, `')'`, and `' '`.
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- `s` represents a valid expression.
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- `'+'` is **not** used as a unary operation (i.e., `"+1"` and `"+(2 + 3)"` is invalid).
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- `'-'` could be used as a unary operation (i.e., `"-1"` and `"-(2 + 3)"` is valid).
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- There will be no two consecutive operators in the input.
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- Every number and running calculation will fit in a signed 32-bit integer.

‎leetcode/basic_calculator/__init__.py‎

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‎leetcode/basic_calculator/playground.ipynb‎

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{
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"cells": [
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "imports",
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"metadata": {},
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"outputs": [],
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"source": [
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"from solution import Solution"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "setup",
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"metadata": {},
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"outputs": [],
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"source": [
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"# Example test case\n",
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"s = \"(1+(4+5+2)-3)+(6+8)\"\n",
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"expected = 23"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "execute",
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"metadata": {},
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"outputs": [],
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"source": [
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"result = Solution().calculate(s)\nresult"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "test",
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"metadata": {},
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"outputs": [],
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"source": [
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"assert result == expected"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "leetcode-py-py3.13",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python3",
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"pygments_lexer": "ipython3",
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"version": "3.13.7"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

‎leetcode/basic_calculator/solution.py‎

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class Solution:
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# Time: O(n)
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# Space: O(n)
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def calculate(self, s: str) -> int:
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stack = []
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num = 0
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sign = 1
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result = 0
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for char in s:
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if char.isdigit():
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num = num * 10 + int(char)
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elif char in "+-":
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result += sign * num
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num = 0
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sign = 1 if char == "+" else -1
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elif char == "(":
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stack.append(result)
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stack.append(sign)
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result = 0
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sign = 1
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elif char == ")":
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if len(stack) < 2:
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raise ValueError("Mismatched parentheses")
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result += sign * num
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num = 0
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result *= stack.pop()
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result += stack.pop()
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elif char != " ":
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raise ValueError(f"Invalid character: '{char}'")
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if stack:
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raise ValueError("Mismatched parentheses")
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return result + sign * num
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# Example walkthrough: "(1+(4+5+2)-3)+(6+8)" = 23
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#
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# char | num | sign | result | stack | action
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# -----|-----|------|--------|------------|------------------
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# '(' | 0 | 1 | 0 | [0, 1] | push result=0, sign=1
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# '1' | 1 | 1 | 0 | [0, 1] | build num=1
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# '+' | 0 | 1 | 1 | [0, 1] | result += 1*1 = 1
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# '(' | 0 | 1 | 0 | [0,1,1,1] | push result=1, sign=1
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# '4' | 4 | 1 | 0 | [0,1,1,1] | build num=4
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# '+' | 0 | 1 | 4 | [0,1,1,1] | result += 1*4 = 4
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# '5' | 5 | 1 | 4 | [0,1,1,1] | build num=5
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# '+' | 0 | 1 | 9 | [0,1,1,1] | result += 1*5 = 9
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# '2' | 2 | 1 | 9 | [0,1,1,1] | build num=2
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# ')' | 0 | 1 | 11 | [0, 1] | result=11*1+1 = 12
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# '-' | 0 | -1 | 12 | [0, 1] | sign = -1
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# '3' | 3 | -1 | 12 | [0, 1] | build num=3
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# ')' | 0 | 1 | 9 | [] | result=9*1+0 = 9
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# '+' | 0 | 1 | 9 | [] | sign = 1
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# '(' | 0 | 1 | 0 | [9, 1] | push result=9, sign=1
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# '6' | 6 | 1 | 0 | [9, 1] | build num=6
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# '+' | 0 | 1 | 6 | [9, 1] | result += 1*6 = 6
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# '8' | 8 | 1 | 6 | [9, 1] | build num=8
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# ')' | 0 | 1 | 14 | [] | result=14*1+9 = 23
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# end | 0 | 1 | 14 | [] | return 14+1*0 = 23

‎leetcode/basic_calculator/tests.py‎

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import pytest
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from leetcode_py.test_utils import logged_test
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from .solution import Solution
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class TestBasicCalculator:
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def setup_method(self):
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self.solution = Solution()
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@pytest.mark.parametrize(
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"s, expected",
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[
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("1 + 1", 2),
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(" 2-1 + 2 ", 3),
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("(1+(4+5+2)-3)+(6+8)", 23),
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("1", 1),
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("-1", -1),
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("-(1+2)", -3),
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("2147483647", 2147483647),
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("1-1+1", 1),
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# Additional edge cases
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("0", 0),
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("-0", 0),
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("()", 0),
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("((()))", 0),
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("1+(2+3)", 6),
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("(1+2)+3", 6),
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("1-(2+3)", -4),
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("(1-2)+3", 2),
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("-(-1)", 1),
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("-(-(-1))", -1),
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("1000000-999999", 1),
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("10+20-30+40", 40),
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("((1+2)+(3+4))", 10),
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("1+(2-(3+4))", -4),
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("-(1+(2+3))", -6),
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(" 1 + 2 ", 3),
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("123+456", 579),
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("-2147483648", -2147483648),
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],
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)
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@logged_test
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def test_calculate(self, s: str, expected: int):
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result = self.solution.calculate(s)
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assert result == expected
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@pytest.mark.parametrize(
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"s, error_msg",
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[
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("(1+2", "Mismatched parentheses"),
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("1+2)", "Mismatched parentheses"),
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("((1+2)", "Mismatched parentheses"),
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("1+2))", "Mismatched parentheses"),
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("1*2", r"Invalid character: '\*'"),
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("1/2", "Invalid character: '/'"),
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("1%2", "Invalid character: '%'"),
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("1^2", r"Invalid character: '\^'"),
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("1&2", "Invalid character: '&'"),
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("a+b", "Invalid character: 'a'"),
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("1+2.5", r"Invalid character: '\.'"),
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],
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)
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@logged_test
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def test_calculate_invalid_input(self, s: str, error_msg: str):
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with pytest.raises(ValueError, match=error_msg):
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self.solution.calculate(s)

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