diff --git a/lib/linked_list.rb b/lib/linked_list.rb index 0de1ee00..1b46c8ae 100644 --- a/lib/linked_list.rb +++ b/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 @@ -18,71 +17,173 @@ 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 + current_index = 0 + current_value = @head.data + while (current_index < (self.length) && !current.nil?) + if current_value == value + return true + elsif current_index != (self.length - 1) + current = current.next + current_value = current.data + current_index += 1 + else + return false + end + end end # method to return the max value in the linked list # returns the data value and not the node def find_max - raise NotImplementedError + return nil if @head.nil? + + current = @head + current_index = 0 + max_value = @head.data + current_value = @head.data + while (current_index < (self.length) && !current.nil?) + if current.data > max_value + max_value = current_value + end + if current.next.nil? + return max_value + end + current = current.next + current_value = current.data + current_index += 1 + end + return max_value 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 + current_index = 0 + min_value = @head.data + current_value = @head.data + while (current_index < (self.length) && !current.nil?) + if current.data < min_value + min_value = current_value + end + if current.next.nil? + return min_value + end + current = current.next + current_value = current.data + current_index += 1 + end + return min_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 + return 0 if @head.nil? + + current = @head + count = 0 + 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 - end + return nil if @head.nil? + return nil if index > self.length + + current = @head + current_index = 0 + while (current_index < index && !current.nil?) + current_index += 1 + current = current.next + 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 + return nil if @head.nil? + + current = @head + current_index = 0 + while (current_index < self.length && !current.nil?) + print current.data + current_index += 1 + 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 node is node to be deleted, change head + if @head.data == value + @head = @head.next + end + + current = @head + while !current.next.nil? + if current.next.data == value + current.next = current.next.next + return + 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 + current = @head + previous = nil + temp = current.next + + until current.nil? + temp = current.next + + current.next = previous + + previous = current + current = temp + end + + @head = previous end @@ -118,7 +219,8 @@ 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