Liv - Space

lib/linked_list.rb

@@ -18,71 +18,158 @@ 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: o1
+    # Space Complexity: o1
     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: o1
+    # Space Complexity: o1
     def search(value)
-      raise NotImplementedError
+      current = @head
+
+      while current
+        if current.data == value 
+          return true
+        end
+        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
+    #Time Complexity: on
+    # Space Complexity: o1
     def find_max
-      raise NotImplementedError
+      return nil if @head == nil
+
+      current = @head
+      max = @head.data
+
+      while current
+        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
+        if current.data < min
+          min = current.data 
+        end
+        current = current.next
+      end
+
+      return min
     end
 
 
     # method that returns the length of the singly linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: on
+    # Space Complexity: o1
     def length
-      raise NotImplementedError
+      current = @head
+      count = 0
+
+      while current != nil
+        count += 1
+        current = current.next
+      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: on
+    # Space Complexity: o1
     def get_at_index(index)
-      raise NotImplementedError
+      current = @head
+      count = 0
+
+      until current.nil?
+        return current.data if count == index
+        current = current.next
+        count += 1
+      end
+
+      return nil
     end
 
     # method to print all the values in the linked list
     # Time Complexity: ?
     # Space Complexity: ?
     def visit
-      raise NotImplementedError
+      print @head.data if @head.next == nil
+
+      current = @head 
+
+      while current
+        print current.data
+        current = current.next
+      end 
     end
 
     # method to delete the first node found with specified value
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: on
+    # Space Complexity: o1
     def delete(value)
-      raise NotImplementedError
+      return nil if @head.nil?
+
+      if @head.data == value
+        @head = @head.next
+        return
+      end
+
+      previous = @head 
+      current = @head.next 
+
+      until current.nil? || current.data == value
+        previous = current
+        current = current.next
+      end
+
+      previous.next = current.next
     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: on
+    # Space Complexity: o1
     def reverse
-      raise NotImplementedError
+      return nil if @head == nil
+
+      current = @head
+      subsequent = nil
+      previous = nil
+
+      while current
+        subsequent = current.next
+        current.next = previous
+        previous = current
+        current = subsequent
+      end
+
+      @head = previous
     end
 
 
@@ -91,7 +178,9 @@ def reverse
     # Time Complexity: ?
     # Space Complexity: ?
     def find_middle_value
-      raise NotImplementedError
+      length = self.length
+      mid = length/2
+      return get_at_index(mid)
     end
 
     # find the nth node from the end and return its value
@@ -118,21 +207,38 @@ def has_cycle
     # Time Complexity: ?
     # Space Complexity: ?
     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: ?
     def add_last(value)
-      raise NotImplementedError
+      return nil if @head == nil
+
+      current = @head
+
+      return self.add_first(data) if current == nil
+      while current.next != nil
+        current = current.next
+      end
+
+      current.next = Node.new(value)
     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: ?
     def get_last
+      current = @head
+
+      while current.next != nil
+        current = current.next
+      end
+
+      return current.data
       raise NotImplementedError
     end