Linked List - Gessica

lib/linked_list.rb

@@ -18,95 +18,204 @@ 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
+      # raise NotImplementedError
+      @head = Node.new(value, @head)
     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
+      # raise NotImplementedError
+      current = @head
+
+      until current == nil
+        if current.data == value
+          return true
+        else
+          current = current.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: O(n)
+    # Space Complexity: O(1)
     def find_max
-      raise NotImplementedError
+      # raise NotImplementedError
+      return nil if @head.nil?
+
+      max_value = @head.data
+      current = @head
+
+      until current == nil
+        if current.data > max_value
+          max_value = current.data
+        end
+        current = current.next
+      end
+
+      return max_value
+
     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
+      # raise NotImplementedError
+      return nil if @head.nil?
+
+      min_value = @head.data
+      current = @head
+
+      until current == nil
+        if current.data < min_value
+          min_value = current.data
+        end
+        current = current.next
+      end
+
+      return min_value
+
     end
 
 
     # 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
+      # raise NotImplementedError
+      return @head.nil? ? nil : @head.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
+      # raise NotImplementedError
+      if @head.nil?
+        @head = Node.new(value)
+      else
+        current = @head
+        until current.next.nil?
+          current = current.next
+        end
+        current.next = Node.new(value)
+      end
     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
+      # raise NotImplementedError
+      count = 0
+      current = @head
+      until current.nil?
+        current = current.next
+        count += 1
+      end
+      return count
     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
+      # raise NotImplementedError
+      counter = 0
+      current = @head
+      until current.nil?
+        if index == counter
+          return current.data
+        else
+          counter += 1
+          current = current.next
+        end
+      end
     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
+      # raise NotImplementedError
+      return nil if @head.nil?
+
+      current = @head
+      until current.nil?
+        puts current.data
+      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
+      # raise NotImplementedError
+      return nil if @head.nil?
+
+      if @head.data == value
+        @head = @head.next
+      else
+        current = @head
+        until current.next.data == value
+          current = current.next
+        end
+        current.next = current.next.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
+      # raise NotImplementedError
+      return nil if @head.nil?
+
+      current = @head
+      prev = nil
+
+      while current
+        temp = current.next
+        current.next = prev
+        prev = current
+        current = temp
+      end
+      @head = prev
+
     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
+      # raise NotImplementedError
+      return nil if @head.nil?
+
+      current = @head
+      until current.next.nil?
+        current = current.next
+      end
+
+      return current.data
     end
 
     ## Advanced Exercises

test/linked_list_test.rb

@@ -103,7 +103,7 @@
         end
     end
 
-    xdescribe "Optional addLast & getLast" do
+    describe "Optional addLast & getLast" do
         it "will add to the front if the list is empty" do
             @list.add_last(1)
             expect(@list.get_at_index(0)).must_equal 1