Merge pull request #1522 from ivanpenaloza/january20

adding algo

Author: ivanpenaloza

src/my_project/interviews/top_150_questions_round_22/ex_54_basic_calculator.py

@@ -0,0 +1,50 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution: 
+
+    def calculate(self, s: str) -> int:
+        """
+        Evaluate a basic calculator expression with +, -, and parentheses.
+        Uses a stack to handle nested parentheses.
+        
+        Time: O(n), Space: O(n)
+        """
+        stack = []
+        result = 0
+        current_num = 0
+        sign = 1  # 1 for positive, -1 for negative
+        
+        for char in s:
+            if char.isdigit():
+                # Build multi-digit number
+                current_num = current_num * 10 + int(char)
+            elif char == '+':
+                # Add previous number with its sign
+                result += sign * current_num
+                current_num = 0
+                sign = 1
+            elif char == '-':
+                # Add previous number with its sign
+                result += sign * current_num
+                current_num = 0
+                sign = -1
+            elif char == '(':
+                # Save current result and sign to stack
+                stack.append(result)
+                stack.append(sign)
+                # Reset for new sub-expression
+                result = 0
+                sign = 1
+            elif char == ')':
+                # Complete current number
+                result += sign * current_num
+                current_num = 0
+                # Pop sign and previous result from stack
+                result *= stack.pop()  # Apply sign before parenthesis
+                result += stack.pop()  # Add previous result
+        
+        # Add the last number
+        result += sign * current_num
+        
+        return result

src/my_project/interviews_typescript/top_150_questions_round_1/test_54_basic_calculator_round_22.ts

@@ -0,0 +1,43 @@
+function calculate(s: string): number {
+    const stack: number[] = [];
+    let result = 0;
+    let currentNum = 0;
+    let sign = 1;  // 1 for positive, -1 for negative
+    
+    for (const char of s) {
+        if (char >= '0' && char <= '9') {
+            // Build multi-digit number
+            currentNum = currentNum * 10 + parseInt(char);
+        } else if (char === '+') {
+            // Add previous number with its sign
+            result += sign * currentNum;
+            currentNum = 0;
+            sign = 1;
+        } else if (char === '-') {
+            // Add previous number with its sign
+            result += sign * currentNum;
+            currentNum = 0;
+            sign = -1;
+        } else if (char === '(') {
+            // Save current result and sign to stack
+            stack.push(result);
+            stack.push(sign);
+            // Reset for new sub-expression
+            result = 0;
+            sign = 1;
+        } else if (char === ')') {
+            // Complete current number
+            result += sign * currentNum;
+            currentNum = 0;
+            // Pop sign and previous result from stack
+            result *= stack.pop()!;  // Apply sign before parenthesis
+            result += stack.pop()!;  // Add previous result
+        }
+        // Skip spaces
+    }
+    
+    // Add the last number
+    result += sign * currentNum;
+    
+    return result;
+}

tests/test_150_questions_round_22/test_54_basic_calculator_round_22.py

@@ -0,0 +1,23 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_22\
+.ex_54_basic_calculator import Solution
+
+class BasicCalculatorTestCase(unittest.TestCase):
+
+    def test_first_pattern(self):
+        solution = Solution()
+        output = solution.calculate(s = "1 + 1")
+        target = 2
+        self.assertEqual(output, target)
+
+    def test_second_pattern(self):
+        solution = Solution()
+        output = solution.calculate(s = " 2-1 + 2 ")
+        target =  3
+        self.assertEqual(output, target)
+
+    def test_third_pattern(self):
+        solution = Solution()
+        output = solution.calculate(s = "(1+(4+5+2)-3)+(6+8)")
+        target =  23
+        self.assertEqual(output, target)