Merge pull request #746 from fartem/284_Peeking_Iterator

2024-10-10 v. 6.7.9: added "284. Peeking Iterator"

Author: fartem

README.md

@@ -544,3 +544,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 237. Delete Node in a Linked List                               | [Link](https://leetcode.com/problems/delete-node-in-a-linked-list/)                               | [Link](./lib/medium/237_delete_node_in_a_linked_list.rb)                               | [Link](./test/medium/test_237_delete_node_in_a_linked_list.rb)                               |
 | 238. Product of Array Except Self                               | [Link](https://leetcode.com/problems/product-of-array-except-self/)                               | [Link](./lib/medium/238_product_of_array_except_self.rb)                               | [Link](./test/medium/test_238_product_of_array_except_self.rb)                               |
 | 240. Search a 2D Matrix II                                      | [Link](https://leetcode.com/problems/search-a-2d-matrix-ii/)                                      | [Link](./lib/medium/240_search_a_2d_matrix_ii.rb)                                      | [Link](./test/medium/test_240_search_a_2d_matrix_ii.rb)                                      |
+| 284. Peeking Iterator                                           | [Link](https://leetcode.com/problems/peeking-iterator/)                                           | [Link](./lib/medium/284_peeking_iterator.rb)                                           | [Link](./test/medium/test_284_peeking_iterator.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 = '6.7.8'
+  s.version = '6.7.9'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/284_peeking_iterator.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/peeking-iterator/
+class PeekingIterator
+  # @param {Iterator} iter
+  def initialize(iter)
+    @iterator = iter
+    @next = @iterator.next
+  end
+
+  # Returns true if the iteration has more elements.
+  # @return {Integer}
+  def has_next = !@next.nil?
+
+  # Returns the next element in the iteration.
+  # @return {Integer}
+  def next
+    tmp = @next
+    @next = @iterator.has_next ? @iterator.next : nil
+
+    tmp
+  end
+
+  # Returns the next element in the iteration without advancing the iterator.
+  # @return {Integer}
+  def peek = @next
+end
+
+# Iterator
+class Iterator
+  # @param {Array} v
+  def initialize(v)
+    @arr = v
+    @curr = 0
+  end
+
+  # @return {Boolean}
+  def has_next = @arr.size > @curr
+
+  # @return {Integer}
+  def next
+    tmp = @arr[@curr]
+    @curr += 1
+
+    tmp
+  end
+end

test/medium/test_284_peeking_iterator.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/284_peeking_iterator'
+require 'minitest/autorun'
+
+class PeekingIteratorTest < ::Minitest::Test
+  def test_default_one
+    peeking_iterator = ::PeekingIterator.new(
+      ::Iterator.new([1, 2, 3])
+    )
+
+    assert_equal(1, peeking_iterator.next)
+    assert_equal(2, peeking_iterator.peek)
+    assert_equal(2, peeking_iterator.next)
+    assert_equal(3, peeking_iterator.next)
+
+    assert(!peeking_iterator.has_next)
+  end
+end