Ida - Fire - Linked Lists

lib/linked_list.rb

@@ -18,65 +18,124 @@ 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 is nil
+      @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
+      current_node = @head
+
+      while current_node
+        if current_node.data == value
+          return true
+        else
+          current_node = current_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: O(n)
+    # Space Complexity: O(1)
     def find_max
-      raise NotImplementedError
+      current_node = @head
+      return if @head.nil?
+      max = current_node.data
+
+      while current_node.next
+        if current_node.next.data > max
+          max = current_node.next.data 
+        end
+        current_node = current_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
+      current_node = @head
+      return if @head.nil?
+      min = current_node.data
+
+      while current_node.next
+        if current_node.next.data < min
+          min = current_node.next.data 
+        end
+        current_node = current_node.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
+      @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
+      return add_first(value) if @head.nil? #if list is empty, adding to the first of the list is the same as adding to the end of the list
+
+      node = @head
+      while !node.next.nil? #when next is nil, we are at the end of the list
+        next_node = node.next
+        node = next_node
+      end
+
+      node.next = Node.new(value)
     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
+      count = 0
+      node = @head
+
+      while !node.nil?
+        count += 1
+        next_node = node.next
+        node = next_node
+      end
+      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
+      node = @head
+      while count < index
+        return if node.nil?
+        node = node.next
+        count += 1
+      end
+
+      node.data
     end
 
     # method to print all the values in the linked list
@@ -87,10 +146,22 @@ def visit
     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
+      return if @head.nil?
+      current_node = @head
+
+      if current.data == value
+        @head = current.next
+      else
+        while (current.next != nil) && (current.next.data != value)
+          current = current.next
+        end
+        unless current.next == nil
+          current.next =current.next.next
+        end
+      end
     end
 
     # method to reverse the singly linked list
@@ -106,7 +177,14 @@ def reverse
     # Time Complexity: ?
     # Space Complexity: ?
     def get_last
-      raise NotImplementedError
+      return if @head.nil?
+
+      node = @head #node is the current object
+      while !node.next.nil? #iterating through objects until node.next is nil
+        # next_node = node.next
+        node = node.next
+      end
+      node.data
     end
 
     ## Advanced Exercises

test/linked_list_test.rb

@@ -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
 
@@ -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