Ports - Jillianne

lib/linked_list.rb

@@ -18,132 +18,279 @@ 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
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity:  O(1)
+    # Space Complexity: O(1)
     def add_first(value)
-      raise NotImplementedError
+      node = Node.new(value, @head)
+      @head = node
     end
 
     # method to find if the linked list contains a node with specified value
     # returns true if found, false otherwise
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity:  O(n)
+    # Space Complexity: O(1)
     def search(value)
-      raise NotImplementedError
+      node = @head
+
+      until node == nil
+        if node == value
+          return true
+        else
+          node = node.next
+        end
+      end
+
+      return false
     end
 
     # method to return the max value in the linked list
     # returns the data value and not the node
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity:  O(n)
+    # Space Complexity: O(1)
     def find_max
-      raise NotImplementedError
+      return nil if @head == nil
+
+      node = @head
+      max = node.data
+
+      until node == nil
+        if node.data > max
+          max = node.data
+        end
+          node = node.next
+      end
+
+      return max
     end
 
     # method to return the min value in the linked list
     # returns the data value and not the node
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity:  O(n)
+    # Space Complexity: O(1)
     def find_min
-      raise NotImplementedError
+      return nil if @head == nil
+
+      node = @head
+      min = node.data
+
+      until node == nil
+        if node.data < min
+          min = node.data
+        end
+          node = node.next
+      end
+
+      return min
     end
 
 
     # method that returns the length of the singly linked list
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity:  O(n)
+    # Space Complexity: O(1)
     def length
-      raise NotImplementedError
+      length = 0
+      node = @head
+
+      until node == nil
+        length += 1
+        node = node.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
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity:  O(n)
+    # Space Complexity: O(1)
     def get_at_index(index)
-      raise NotImplementedError
+      value = nil
+      node = @head
+      i = 0
+
+      until node == nil
+        if i == index
+          value = node.data
+          break
+        end
+        node = node.next
+        i += 1
+      end
+
+      return value
     end
 
     # method to print all the values in the linked list
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity:  O(n)
+    # Space Complexity: O(1)
     def visit
-      raise NotImplementedError
+      return nil if @head == nil
+      node = @head
+
+      until node == nil
+        puts node.data
+        node = node.next
+      end
     end
 
     # method to delete the first node found with specified value
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def delete(value)
-      raise NotImplementedError
+      node = @head
+
+      until node == nil
+        if node.data == value
+          @head = node.next
+          break
+        elsif node.next.data == value
+          node.next = node.next.next
+          break
+        end
+        node = node.next
+      end
     end
 
     # method to reverse the singly linked list
     # note: the nodes should be moved and not just the values in the nodes
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def reverse
-      raise NotImplementedError
+      # 3 (head) -> 2 (tail) -> nil
+      return nil if !@head
+
+      previous = nil
+      current = @head
+
+      until !current
+        next_node = current.next # 2, nil
+        current.next = previous # nil, 3 @head
+        previous = current # 3 @head, 2
+        current = next_node # 2, nil
+      end
+
+      @head = previous  #2
     end
 
 
     ## Advanced Exercises
     # returns the value at the middle element in the singly linked list
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity: O(2n) -> O(n)
+    # Space Complexity: O(1)
     def find_middle_value
-      raise NotImplementedError
+      return nil if !@head
+
+      node = @head 
+
+      length = self.length - 1
+      length = (length / 2.0).ceil
+
+      length.times do 
+        node = node.next
+      end
+
+      return node.data
     end
 
     # find the nth node from the end and return its value
     # assume indexing starts at 0 while counting to n
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity: O(2n) -> O(n)
+    # Space Complexity: O(1)
     def find_nth_from_end(n)
-      raise NotImplementedError
+      length = self.length
+      return nil if !(length > n)
+
+      node = @head
+
+      while n < length - 1
+        node = node.next
+        n += 1
+      end
+
+      return node.data
     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.
-    # Time Complexity:  
+    # Time Complexity:
     # Space Complexity
     def has_cycle
       raise NotImplementedError
     end
 
 
-    # Additional Exercises 
+    # Additional Exercises
     # returns the value in the first node
     # returns nil if the list is empty
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity: O(1)
+    # Space Complexity: O(1)
     def get_first
-      raise NotImplementedError
+      node = @head
+
+      return node == nil ? nil : node.data
     end
 
     # method that inserts a given value as a new last node in the linked list
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def add_last(value)
-      raise NotImplementedError
+      node = @head
+
+      if node == nil
+        @head = Node.new(value)
+      else
+        until node.next == nil
+          node = node.next
+        end
+
+        node.next = Node.new(value)
+      end
     end
 
     # method that returns the value of the last node in the linked list
     # returns nil if the linked list is empty
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def get_last
-      raise NotImplementedError
+      node = @head
+
+      return nil if node == nil
+
+      until node.next == nil
+        node = node.next
+      end
+
+      return node.data
     end
 
     # method to insert a new node with specific data value, assuming the linked
     # list is sorted in ascending order
-    # Time Complexity:  
-    # Space Complexity
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def insert_ascending(value)
-      raise NotImplementedError
+      node = @head
+
+      if node == nil
+        @head = Node.new(value)
+      elsif node.data > value
+        @head = Node.new(value, node)
+      else
+        while node.data < value
+          if node.next != nil
+            if node.next.data > value
+              connected_node = node.next
+              node.next = Node.new(value, connected_node)
+              break
+            end
+            node = node.next
+          else
+            node.next = Node.new(value)
+            break
+          end
+        end
+      end
     end
 
     # Helper method for tests
@@ -160,4 +307,4 @@ def create_cycle
 
       current.next = @head # make the last node link to first node
     end
-end
+end

test/linked_list_test.rb

@@ -15,7 +15,6 @@
 
     describe 'initialize' do
         it 'can be created' do
-
             # Assert
             expect(@list).must_be_kind_of LinkedList
         end