sai's linked list

linked_list.rb

@@ -19,77 +19,232 @@ 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 insert(value)
-    puts "Not implemented"
+    node = Node.new(value)
+    if @head == nil
+      @head = node
+    else
+      node.next = @head
+      @head = node
+    end
+
+    # puts "Not implemented"
   end
 
   # method to find if the linked list contains a node with specified value
   # returns true if found, false otherwise
   def search(value)
-    puts "Not implemented"
+    current = @head
+    while current != nil
+      if current.data == value
+        return true
+      else
+        current = current.next
+      end
+
+    end
+    return false
+
+    # puts "Not implemented"
   end
 
   # method to return the max value in the linked list
   # returns the data value and not the node
   def find_max
-    puts "Not implemented"
+
+    current = @head
+    max = current.data
+    while current != nil
+      if current.data > max
+        max = current.data
+      else
+        current = current.next
+      end
+    end
+    return max
+    # puts "Not implemented"
   end
 
   # method to return the min value in the linked list
   # returns the data value and not the node
   def find_min
-    puts "Not implemented"
+    current = @head
+    min = current.data
+    while current != nil
+      if current.data < min
+        min = current.data
+      else
+        current = current.next
+      end
+    end
+    return min
+    # puts "Not implemented"
   end
 
   # method that returns the length of the singly linked list
   def length
-    puts "Not implemented"
+    return 0 if @head == nil
+    current = @head
+    size = 0
+    while current != nil do
+      size += 1
+      current = current.next
+    end
+    return size
   end
 
   # method to return the value of the nth element from the beginning
   # assume indexing starts at 0 while counting to n
   def find_nth_from_beginning(n)
-    puts "Not implemented"
+    current = @head
+    size = 0
+    until size == n do
+      size += 1
+      current = current.next
+    end
+    return current.data
   end
 
   # method to insert a new node with specific data value, assuming the linked
   # list is sorted in ascending order
   def insert_ascending(value)
-    puts "Not implemented"
+    node = Node.new(value)
+    current = @head
+    # puts "helloooo #{current.data}"
+    # puts "Value: #{value}"
+    inserted = false
+    while current != nil && !inserted do
+      # puts "Count: #{count}"
+      if current.data < value
+        # puts "Current.data: #{current.data}"
+        if current.next == nil
+          # puts "Reached the end"
+          current.next = node
+          inserted = true
+        elsif current.next.data > value
+          # puts "Found the magic spot"
+          node.next = current.next
+          current.next = node
+          inserted = true
+        else
+          current = current.next
+        end
+      else
+        current = current.next
+      end
+    end
+
+    # puts "Not implemented"
   end
 
   # method to print all the values in the linked list
   def visit
-    puts "Not implemented"
+    current = @head
+    while current != nil do
+        print "#{current.data}  "
+        current = current.next
+    end
+    puts
+    # puts "Not implemented"
   end
 
   # method to delete the first node found with specified value
   def delete(value)
-    puts "Not implemented"
+    return if @head == nil
+    if @head.data == value
+      @head = @head.next
+    else
+      current = @head
+      while current.next != nil do
+        if current.next.data == value
+            current.next = current.next.next
+        else
+          current = current.next
+        end
+      end
+    end
+
   end
 
   # method to reverse the singly linked list
   # note: the nodes should be moved and not just the values in the nodes
   def reverse
-    puts "Not implemented"
+    current = @head
+    previous = nil
+
+    until current == nil do
+      temp = current.next
+      current.next = previous
+      previous = current
+      current = temp
+    end
+    @head = previous
+    # puts "Not implemented"
   end
 
   ## Advanced Exercises
   # returns the value at the middle element in the singly linked list
   def find_middle_value
-    puts "Not implemented"
+    return if @head == nil
+    return @head.data if @head.next == nil
+
+    slow = @head
+    fast = @head.next
+
+    while fast != nil do
+      slow = slow.next
+      fast = fast.next
+      if fast != nil
+        fast = fast.next
+      end
+    end
+    return slow.data
+    # puts "Not implemented"
   end
 
   # find the nth node from the end and return its value
   # assume indexing starts at 0 while counting to n
   def find_nth_from_end(n)
-    puts "Not implemented"
+    return if @head == nil
+    i = 0
+    current = @head
+
+    until i == n do
+      current = current.next
+      i += 1
+    end
+
+    trailing_current = @head
+    # puts "current: #{current.data}"
+    # puts "trailing: #{trailing_current.data}"
+    until current.next == nil do
+      current = current.next
+      trailing_current = trailing_current.next
+      # puts "current: #{current.data}"
+      # puts "trailing: #{trailing_current.data}"
+    end
+
+    # puts "****Trailing: #{trailing_current.data}"
+    return trailing_current.data# puts "Not implemented"
   end
 
   # checks if the linked list has a cycle. A cycle exists if any node in the
   # linked list links to a node already visited.
   # returns true if a cycle is found, false otherwise.
   def has_cycle
-    puts "Not implemented"
+    return false if @head == nil
+    return false if @head.next == nil
+
+    slow = @head
+    fast = @head
+
+    while fast != nil do
+      slow = slow.next
+      fast = fast.next
+      fast = fast.next if fast != nil
+      return true if fast == slow
+    end
+    return false
+    # puts "Not implemented"
   end
 
   # Creates a cycle in the linked list for testing purposes
@@ -112,6 +267,7 @@ def create_cycle
 # Create an object of linked list class
 my_linked_list = LinkedList.new()
 
+puts "\n*******  Add Values to List *******"
 # Add some values to the linked list
 puts "Adding 5, 3 and 1 to the linked list."
 my_linked_list.insert(5)
@@ -122,6 +278,7 @@ def create_cycle
 puts "Printing elements in the linked list:"
 my_linked_list.visit
 
+puts "\n*******  Find Value at Nth Node *******"
 # Find the value at the nth node
 puts "Confirming values in the linked list using find_nth_from_beginning method."
 value = my_linked_list.find_nth_from_beginning(2)
@@ -134,10 +291,13 @@ def create_cycle
 # print all elements
 puts "Printing elements in the linked list:"
 my_linked_list.visit
+puts "length #{my_linked_list.length}"
 
+puts "\n*******  Insert Ascending *******"
 # Insert ascending
 puts "Adding 4 in ascending order."
 my_linked_list.insert_ascending(4)
+
 # check newly inserted value
 puts "Checking values by calling find_nth_from_beginning method."
 value = my_linked_list.find_nth_from_beginning(2)
@@ -160,13 +320,16 @@ def create_cycle
 my_linked_list_length = my_linked_list.length
 puts "BUG: Length should be 5 and not #{my_linked_list_length}" if my_linked_list_length != 5
 
+
+puts "\n*******  Find Min & Max *******"
 # find min and max
 puts "Confirming min and max values in the linked list."
 min = my_linked_list.find_min
 puts "BUG: Min value should be 1 and not #{min}" if min != 1
 max = my_linked_list.find_max
 puts "BUG: Max value should be 5 and not #{max}" if max != 6
 
+puts "\n*******  Delete Value *******"
 # delete value
 puts "Deleting node with value 5 from the linked list."
 my_linked_list.delete(5)
@@ -189,11 +352,13 @@ def create_cycle
 my_linked_list_length = my_linked_list.length
 puts "BUG: Length should be 3 and not #{my_linked_list_length}" if my_linked_list_length != 3
 
+puts "\n*******  Find Middle Element *******"
 # find middle element
 puts "Confirming middle value in the linked list."
 middle = my_linked_list.find_middle_value
 puts "BUG: Middle value should be 4 and not #{middle}" if middle != 4
 
+puts "\n*******  Reverse Linked List *******"
 # reverse the linked list
 puts "Reversing the linked list."
 my_linked_list.reverse
@@ -209,6 +374,7 @@ def create_cycle
 value = my_linked_list.find_nth_from_beginning(0)
 puts "BUG: Value at index 0 should be 6 and is #{value}" if value != 6
 
+puts "\n*******  Find Nth From End *******"
 # nth from the end
 puts "Verifying find_nth_from_end method."
 value = my_linked_list.find_nth_from_end(0)
@@ -218,6 +384,7 @@ def create_cycle
 value = my_linked_list.find_nth_from_end(2)
 puts "BUG: Value at index 2 from the end, should be 6 and is #{value}" if value != 6
 
+puts "\n*******  Create Cycle *******"
 # check for cycle
 puts "Checking the linked list for cycle."
 puts "BUG: Should not have a cycle." if my_linked_list.has_cycle