adding algos

src/my_project/interviews/top_150_questions_round_22/ex_53_evaluate_reverse_polish_notation.py

@@ -0,0 +1,32 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution:
+    def evalRPN(self, tokens: List[str]) -> int:
+        stack = []
+        operators = ['+', '-', '*', '/']
+
+        for token in tokens:
+            if token in operators:
+                # Pop two operands (note: order matters for - and /)
+                b = stack.pop()
+                a = stack.pop()
+
+                # Apply operation
+                if token == '+':
+                    result = a + b
+                elif token == '-':
+                    result = a - b
+                elif token == '*':
+                    result = a * b
+                else:  # token == '/'
+                    # Truncate toward zero
+                    result = int(a / b)
+
+                stack.append(result)
+            else:
+                # It's a number, push to stack
+                stack.append(int(token))
+
+        # Final result is the only element left in stack
+        return stack[0]

src/my_project/interviews_typescript/top_150_questions_round_1/ex_53_evaluate_reverse_polish_notation.ts

@@ -0,0 +1,33 @@
+function evalRPN(tokens: string[]): number {
+    const stack: number[] = [];
+    const operators: string[] = ['+', '-', '*', '/'];
+
+    for (const token of tokens) {
+        if (operators.includes(token)) {
+            // Pop two operands (note: order matters for - and /)
+            const b = stack.pop()!;
+            const a = stack.pop()!;
+
+            // Apply operation
+            let result: number;
+            if (token === '+') {
+                result = a + b;
+            } else if (token === '-') {
+                result = a - b;
+            } else if (token === '*') {
+                result = a * b;
+            } else { // token === '/'
+                // Truncate toward zero
+                result = Math.trunc(a / b);
+            }
+
+            stack.push(result);
+        } else {
+            // It's a number, push to stack
+            stack.push(parseInt(token));
+        }
+    }
+
+    // Final result is the only element left in stack
+    return stack[0];
+}

tests/test_150_questions_round_22/test_53_evaluate_reverse_polish_notation_round_22.py

@@ -0,0 +1,24 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_22\
+.ex_53_evaluate_reverse_polish_notation import Solution
+
+class EvaluateReversePolishNotationTestCase(unittest.TestCase):
+
+    def test_first_pattern(self):
+        solution = Solution()
+        output = solution.evalRPN(tokens = ["2","1","+","3","*"])
+        target = 9
+        self.assertEqual(output, target)
+
+    def test_second_pattern(self):
+        solution = Solution()
+        output = solution.evalRPN(tokens = ["4","13","5","/","+"])
+        target =  6
+        self.assertEqual(output, target)
+
+    def test_third_pattern(self):
+        solution = Solution()
+        output = solution.evalRPN(tokens = ["10","6","9","3","+","-11",
+                                            "*","/","*","17","+","5","+"])
+        target =  22
+        self.assertEqual(output, target)