Fire - Roshni

lib/linked_list.rb

@@ -1,4 +1,3 @@
-
 # Defines a node in the singly linked list
 class Node
   attr_reader :data # allow external entities to read value but not write
@@ -18,95 +17,199 @@ 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
+      if @head 
+        new_node = Node.new(value)
+        new_node.next = @head 
+        @head = new_node
+      else
+        @head = Node.new(value)
+      end
     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 
+        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 = current.data 
+
+      until 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 = current.data 
+
+      until 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 @head ? @head.data : nil 
     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 
+        current = @head 
+        until current.next.nil? 
+          current = current.next 
+        end
+        current.next = Node.new(value)
+      else 
+        @head = 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
+      length = 0 
+      current = @head 
+
+      while current
+        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 self.length < index || @head.nil? 
+      i = 0 
+      current = @head 
+
+      while current 
+        if i == index 
+          return current.data 
+        else 
+          current = current.next 
+          i += 1 
+        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
+      return nil if @head.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: O(n)
+    # Space Complexity: O(1)
     def delete(value)
-      raise NotImplementedError
+      return nil if @head.nil? 
+
+      if @head.data == value 
+        @head = @head.next 
+        return 
+      else
+        current = @head 
+        while current.next 
+          if current.next.data == value 
+            current.next = current.next.next 
+            return 
+          end
+          current = current.next 
+        end
+      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
+      return nil if @head.nil? 
+
+      current = @head 
+      prev = nil 
+
+      while current
+        temp = current.next 
+        current.next = prev 
+        prev = current 
+        current = temp 
+      end 
+      @head = prev 
+      return @head 
     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
+      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