Leaves - Dominique

lib/linked_list.rb

@@ -1,4 +1,4 @@
-
+require 'pry'
 # Defines a node in the singly linked list
 class Node
   attr_reader :data # allow external entities to read value but not write
@@ -19,54 +19,154 @@ def initialize
     # method to add a new node with the specific data value in the linked list
     # insert the new node at the beginning of the linked list
     def add_first(value)
-      raise NotImplementedError
+      new_node = Node.new(value)
+
+      new_node.next = @head
+
+      @head = new_node 
+      # head is not a node, it is just a variable that refers to the first node
     end
 
     # method to find if the linked list contains a node with specified value
     # returns true if found, false otherwise
     def search(value)
-      raise NotImplementedError
+      current = @head
+
+      until current == nil
+        return true if current.data == value
+        current = current.next 
+      end 
+
+      return false
     end
 
     # method to return the max value in the linked list
     # returns the data value and not the node
     def find_max
-      raise NotImplementedError
+      return nil if @head == nil 
+
+      current = @head 
+      max = current.data
+
+
+      until current == nil
+        max = current.data if current.data > max
+        current = current.next
+      end 
+
+      return max
     end
 
     # method to return the min value in the linked list
     # returns the data value and not the node
     def find_min
-      raise NotImplementedError
-    end
+      return nil if @head == nil
+
+      current = @head 
+      min = current.data
+
 
+      until current == nil
+        min = current.data if current.data < min
+        current = current.next
+      end
+
+      return min
+    end
 
     # method that returns the length of the singly linked list
     def length
-      raise NotImplementedError
+      return 0 if @head == nil
+
+      length = 0
+      current = @head
+      # current 
+
+      until current == nil
+        length += 1
+        current = current.next 
+      end 
+
+      return length
     end
 
     # method that returns the value at a given index in the linked list
     # index count starts at 0
     # returns nil if there are fewer nodes in the linked list than the index value
     def get_at_index(index)
-      raise NotImplementedError
+
+      current = @head
+      value = ''
+
+      return current.data if index == 0
+
+      new_index = index + 1
+
+      new_index.times do |count|
+        return nil if current == nil
+        value = current.data
+        current = current.next
+      end 
+
+      return value 
     end
 
     # method to print all the values in the linked list
     def visit
-      raise NotImplementedError
+      linked_list_array = []
+
+      current = @head 
+
+      until current == nil
+        linked_list_array.push(current.data)
+        current = current.next
+      end
+
+      return linked_list_array
     end
 
     # method to delete the first node found with specified value
     def delete(value)
-      raise NotImplementedError
+
+
+      return nil if @head == nil
+
+      current = @head
+
+      if current.data == value
+        @head = current.next
+        return
+      end
+
+      until current == nil
+        if current.next.data == value
+          current.next == current.next.next
+          return 
+        end 
+
+        current = current.next 
+      end 
+
+      return
     end
 
     # method to reverse the singly linked list
     # note: the nodes should be moved and not just the values in the nodes
     def reverse
-      raise NotImplementedError
+      return if @head.nil?
+
+      current = @head
+      previous = nil
+
+      until current.next.nil?
+        temp = current.next
+        current.next = previous
+        previous = current
+        current = temp
+      end 
+
+      current.next = previous
+      @head = current
     end
 
 
@@ -94,18 +194,39 @@ def has_cycle
     # returns the value in the first node
     # returns nil if the list is empty
     def get_first
-      raise NotImplementedError
+      return nil if @head == nil
+
+      return @head.data
     end
 
     # method that inserts a given value as a new last node in the linked list
     def add_last(value)
-      raise NotImplementedError
+
+      new_node = Node.new(value)
+
+      if @head.nil?
+        add_first(value)
+      else
+        current = @head
+        while current.next != nil
+          current = current.next
+        end
+        current.next = new_node
+      end	   
     end
 
     # method that returns the value of the last node in the linked list
     # returns nil if the linked list is empty
     def get_last
-      raise NotImplementedError
+      return nil if @head.nil?
+
+      current = @head
+
+      while current.next != nil
+        current = current.next
+      end 
+
+      return current.data
     end
 
     # method to insert a new node with specific data value, assuming the linked

test/linked_list_test.rb

@@ -5,6 +5,7 @@
 require_relative 'test_helper'
 
 
+
 Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
 
 describe LinkedList do
@@ -25,7 +26,7 @@
         it 'can add values to an empty list' do
             # Act
             @list.add_first(3)
-
+            
             # Assert
             expect(@list.get_first).must_equal 3
         end
@@ -60,6 +61,7 @@
             expect(@list.search(3)).must_equal true
 
             expect(@list.search(2)).must_equal true
+
         end
 
         it "returns false if the element is not in the list" do
@@ -74,7 +76,7 @@
         end
     end
 
-    describe "length" do
+   describe "length" do
         it "will return 0 for an empty list" do
             expect(@list.length).must_equal 0
         end
@@ -192,7 +194,7 @@
         end
     end
 
-    describe "nth_from_the_end" do
+    xdescribe "nth_from_the_end" do
         it 'returns nil if n is outside the bounds of the list' do
             expect(@list.find_nth_from_end(3)).must_be_nil
         end
@@ -211,6 +213,17 @@
         end
     end
 
+    describe "visit" do
+        it 'can print all the values in the linked list' do
+            @list.add_first(4)
+            @list.add_first(3)
+            @list.add_first(2)
+            @list.add_first(1)
+
+            expect(@list.visit).must_equal [1, 2, 3, 4]
+        end 
+    end 
+
     describe "reverse" do
         it 'can retrieve an item at index n from the end in the list' do
             @list.add_first(4)