2024-12-25 v. 7.4.8: added "707. Design Linked List"

Author: fartem

README.md

@@ -612,3 +612,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 687. Longest Univalue Path                                      | [Link](https://leetcode.com/problems/longest-univalue-path/)                                      | [Link](./lib/medium/687_longest_univalue_path.rb)                                      | [Link](./test/medium/test_687_longest_univalue_path.rb)                                      |
 | 692. Top K Frequent Words                                       | [Link](https://leetcode.com/problems/top-k-frequent-words/)                                       | [Link](./lib/medium/692_top_k_frequent_words.rb)                                       | [Link](./test/medium/test_692_top_k_frequent_words.rb)                                       |
 | 701. Insert into a Binary Search Tree                           | [Link](https://leetcode.com/problems/insert-into-a-binary-search-tree/)                           | [Link](./lib/medium/701_insert_into_a_binary_search_tree.rb)                           | [Link](./test/medium/test_701_insert_into_a_binary_search_tree.rb)                           |
+| 707. Design Linked List                                         | [Link](https://leetcode.com/problems/design-linked-list/)                                         | [Link](./lib/medium/707_design_linked_list.rb)                                         | [Link](./test/medium/test_707_design_linked_list.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 = '7.4.7'
+  s.version = '7.4.8'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/707_design_linked_list.rb

@@ -0,0 +1,118 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/design-linked-list/
+class MyLinkedList
+  # Init
+  def initialize
+    @head = nil
+    @length = 0
+  end
+
+  # @param {Integer} index
+  # @return {Integer}
+  def get(index)
+    return -1 unless is_valid_index(index)
+
+    node_at_index(index).val
+  end
+
+  # @param {Integer} val
+  # @return {Void}
+  def add_at_head(val)
+    new_head = ::MyLinkedList::InnerListNode.new(val)
+    if @head
+      prev = @head
+      @head = new_head
+      new_head.next = prev
+    else
+      @head = new_head
+    end
+
+    @length += 1
+  end
+
+  # @param {Integer} val
+  # @return {Void}
+  def add_at_tail(val)
+    if @head
+      tail = node_at_index(@length - 1)
+      tail&.next = ::MyLinkedList::InnerListNode.new(val)
+    else
+      @head = ::MyLinkedList::InnerListNode.new(val)
+    end
+
+    @length += 1
+  end
+
+  # @param {Integer} index
+  # @param {Integer} val
+  # @return {Void}
+  def add_at_index(index, val)
+    if is_valid_index(index)
+      if index.zero?
+        add_at_head(val)
+      else
+        prev = node_at_index(index - 1)
+        nxt = node_at_index(index)
+        new_node = ::MyLinkedList::InnerListNode.new(val)
+        prev.next = new_node
+        new_node.next = nxt
+      end
+
+      @length += 1
+    elsif index == @length
+      add_at_tail(val)
+    end
+  end
+
+  # @param {Integer} index
+  # @return {Void}
+  def delete_at_index(index)
+    return unless is_valid_index(index)
+
+    if index.zero?
+      if @head
+        @head = @head.next
+        @length -= 1
+      end
+    else
+      prev = node_at_index(index - 1)
+      prev.next = prev.next ? prev.next.next : nil
+      @length -= 1
+    end
+
+    puts(@length)
+  end
+
+  # InnerListNode
+  class InnerListNode
+    attr_accessor :val, :next
+
+    # @param {Integer} val
+    def initialize(val)
+      @val = val
+      @next = nil
+    end
+  end
+
+  private
+
+  # @param {Integer} index
+  # @return {Boolean}
+  def is_valid_index(index) = index >= 0 && index < @length
+
+  # @param {Integer} index
+  # @return {ListNode}
+  def node_at_index(index)
+    return @head if index.zero?
+
+    target = @head
+    position = 0
+    until position == index
+      target = target.next
+      position += 1
+    end
+
+    target
+  end
+end

test/medium/test_707_design_linked_list.rb

@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/707_design_linked_list'
+require 'minitest/autorun'
+
+class DesignLinkedListTest < ::Minitest::Test
+  def test_default_one
+    my_linked_list = ::MyLinkedList.new
+    my_linked_list.add_at_head(1)
+    my_linked_list.add_at_tail(3)
+    my_linked_list.add_at_index(1, 2)
+
+    assert_equal(2, my_linked_list.get(1))
+
+    my_linked_list.delete_at_index(1)
+
+    assert_equal(3, my_linked_list.get(1))
+  end
+
+  def test_additional_one
+    my_linked_list = ::MyLinkedList.new
+    my_linked_list.add_at_tail(1)
+    my_linked_list.add_at_index(0, 1)
+    my_linked_list.delete_at_index(0)
+
+    assert_equal(1, my_linked_list.get(0))
+
+    my_linked_list.add_at_index(2, 2)
+  end
+end