Blaine - LinkedListThursday

lib/linked_list.rb

@@ -18,98 +18,201 @@ 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
+      new_node = Node.new(value)
+      new_node.next = @head
+      @head = new_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
+      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
+      if @head == nil
+        return nil
+      end
+      max_val = @head.data
+      current = @head
+      until current == nil
+        if current.data > max_val
+          max_val = current.data
+        end 
+        current = current.next
+      end
+      return max_val
     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
+      if @head == nil
+        return nil
+      end
+      min_val = @head.data
+      current = @head
+      until current == nil
+        if current.data < min_val
+          min_val = current.data
+        end
+        current = current.next
+      end
+      return min_val
     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: 0(1)
+    # Space Complexity: 0(1)
     def get_first
-      raise NotImplementedError
+      if @head == nil 
+        return nil
+      end
+      @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)
+      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: 0(n)
+    # Space Complexity: O(1)
     def length
-      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
+      count = 0
+      if index > length
+        return nil
+      end
+      current = @head
+      until current == nil
+        if count == index
+          return current.data
+        else
+          count += 1
+          current = current.next
+        end
+      end
+      return current.data
     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
+      current = @head
+      until current.next == 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
+      if @head == nil
+        return nil
+      end
+      if @head.data == value
+        @head = @head.next
+      end
+      current = @head
+      until current.next == nil
+        if current.next.data == value
+          current.next = current.next.next
+        end
+        current = current.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
+      previous = nil
+      current = @head
+      temp = current.next
+      # All variables are pointers
+      until current.next == nil
+        current.next = previous
+        previous = current
+        current = temp
+        temp = current.next
+      end
+      current.next = previous
+      @head = current
+      return
     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
+      if @head == nil
+        return nil
+      else
+      current = @head
+        until current.next == nil
+          current = current.next
+        end
+      end
+      return current.data
     end
-
-    ## Advanced Exercises
+
+###############################################################################################################
+
+  ## Advanced Exercises
     # returns the value at the middle element in the singly linked list
     # Time Complexity: ?
     # Space Complexity: ?

test/linked_list_test.rb

@@ -23,7 +23,7 @@
             @list.add_first(3)
 
             # Assert
-            expect(@list.get_at_index(0)).must_equal 3
+            expect(@list.get_first()).must_equal 3
         end
 
         it 'will put the last added item to the front of the list' do
@@ -32,18 +32,18 @@
             @list.add_first(2)
 
             # Assert
-            expect(@list.get_at_index(0)).must_equal 2
+            expect(@list.get_first()).must_equal 2
 
             # Act again
             @list.add_first(3)
 
             # Assert
-            expect(@list.get_at_index(0)).must_equal 3
+            expect(@list.get_first()).must_equal 3
         end
 
         it 'will return `nil` for `getFirst` if the list is empty' do
 
-            expect(@list.get_at_index(0)).must_be_nil
+            expect(@list.get_first()).must_be_nil
         end
     end
 
@@ -59,10 +59,10 @@
         end
 
         it "returns false if the element is not in the list" do
-          @list = LinkedList.new
-          @list.add_first(3)
-          @list.add_first(2)
-          expect(@list.search("pasta")).must_equal false
+            @list = LinkedList.new
+            @list.add_first(3)
+            @list.add_first(2)
+            expect(@list.search("pasta")).must_equal false
         end
 
         it "returns false for an empty list" do
@@ -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