Water - Leah

lib/linked_list.rb

@@ -18,80 +18,145 @@ 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
+      @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
+      return false if @head == nil
+      current = @head
+      while !current.nil? # while the current node is not 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
+      return nil if @head == nil
+      current = @head
+      max = 0
+      while current != nil
+        if current.data > max
+          max = current.data
+        end
+        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
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def find_min
-      raise NotImplementedError
+      return nil if @head == nil
+      current = @head
+      min = @head.data
+      while current != nil
+        if current.data < min
+          min = current.data
+        end
+        current = current.next
+      end
+      return min
     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
+      return nil if @head == nil
+      return @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
+      if @head == nil
+        @head = Node.new(value, nil)
+        return
+      end
+
+      current = @head
+      until current.next == nil
+        current = current.next
+      end
+      current.next = Node.new(value, nil)
     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
+      return 0 if @head == nil
+      length = 0
+      current = @head
+      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
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def get_at_index(index)
-      raise NotImplementedError
+      return nil if index >= self.length
+      current = @head
+      count = 0
+      if @head.nil? == false
+        until count == index
+          count += 1
+          current = current.next
+        end
+        return current.data
+      end
     end
 
     # method to print all the values in the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1) because each value is printed to console, never saved to a data structure?
     def visit
-      raise NotImplementedError
+      return nil if @head == nil
+      current = @head
+      until current == nil
+        puts current.data
+        current = current.next
+      end
     end
 
     # method to delete the first node found with specified value
     # Time Complexity: ?
     # Space Complexity: ?
-    def delete(value)
-      raise NotImplementedError
-    end
+    # def delete(value)
+    #   return nil if @head == nil
+    #   if @head.data == value
+    #     @head = @head.next
+
+    #   end
+
+    # end
 
     # method to reverse the singly linked list
     # note: the nodes should be moved and not just the values in the nodes
@@ -103,12 +168,17 @@ def reverse
 
     # 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
+      return nil if @head == nil
+      current = @head
+      until current.next == nil
+        current = current.next
+      end
+      return current.data
     end
-
+    #___________________________________________________________________
     ## Advanced Exercises
     # returns the value at the middle element in the singly linked list
     # Time Complexity: ?