2024-08-28 v. 6.5.7: added "150. Evaluate Reverse Polish Notation"

README.md

@@ -522,3 +522,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 146. LRU Cache                                                  | [Link](https://leetcode.com/problems/lru-cache/)                                                  | [Link](./lib/medium/146_lru_cache.rb)                                                  | [Link](./test/medium/test_146_lru_cache.rb)                                                  |
 | 147. Insertion Sort List                                        | [Link](https://leetcode.com/problems/insertion-sort-list/)                                        | [Link](./lib/medium/147_insertion_sort_list.rb)                                        | [Link](./test/medium/test_147_insertion_sort_list.rb)                                        |
 | 148. Sort List                                                  | [Link](https://leetcode.com/problems/sort-list/)                                                  | [Link](./lib/medium/148_sort_list.rb)                                                  | [Link](./test/medium/test_148_sort_list.rb)                                                  |
+| 150. Evaluate Reverse Polish Notation                           | [Link](https://leetcode.com/problems/evaluate-reverse-polish-notation/)                           | [Link](./lib/medium/150_evaluate_reverse_polish_notation.rb)                           | [Link](./test/medium/test_150_evaluate_reverse_polish_notation.rb)                           |

leetcode-ruby.gemspec

@@ -5,7 +5,7 @@ require 'English'
 ::Gem::Specification.new do |s|
   s.required_ruby_version = '>= 3.0'
   s.name = 'leetcode-ruby'
-  s.version = '6.5.6'
+  s.version = '6.5.7'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/150_evaluate_reverse_polish_notation.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+require 'set'
+
+# https://leetcode.com/problems/evaluate-reverse-polish-notation/
+# @param {String[]} tokens
+# @return {Integer}
+def eval_rpn(tokens)
+  ops = ['+', '-', '*', '/'].to_set
+  stack = []
+  tokens.each do |token|
+    if ops.include?(token)
+      b = stack.pop
+      a = stack.pop
+
+      case token
+      when '+'
+        stack << a + b
+      when '-'
+        stack << a - b
+      when '*'
+        stack << a * b
+      when '/'
+        stack << (a.to_f / b).truncate
+      end
+    else
+      stack << token.to_i
+    end
+  end
+
+  stack.pop
+end

test/medium/test_150_evaluate_reverse_polish_notation.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/150_evaluate_reverse_polish_notation'
+require 'minitest/autorun'
+
+class EvaluateReversePolishNotationTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      9,
+      eval_rpn(
+        ['2', '1', '+', '3', '*']
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      6,
+      eval_rpn(
+        ['4', '13', '5', '/', '+']
+      )
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      22,
+      eval_rpn(
+        ['10', '6', '9', '3', '+', '-11', '*', '/', '*', '17', '+', '5', '+']
+      )
+    )
+  end
+
+  def test_additional_one
+    assert_equal(
+      0,
+      eval_rpn(
+        ['2', '2', '-']
+      )
+    )
+  end
+end