diff --git a/lib/linked_list.rb b/lib/linked_list.rb index 0de1ee00..b2518cd1 100644 --- a/lib/linked_list.rb +++ b/lib/linked_list.rb @@ -18,71 +18,148 @@ 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) + if @head.nil? + @head = new_node + else + new_node.next = @head + @head = new_node + 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(1) + # Space Complexity: O(1) def search(value) - raise NotImplementedError + if @head.nil? + return false + end + current = @head + until current.data == value || current.next.nil? + current = current.next + end + return current.data == value end # method to return the max value in the linked list # returns the data value and not the node def find_max - raise NotImplementedError + if @head.nil? + return nil + end + current = @head + max = @head.data + until current.next.nil? + current = current.next + if current.data > max + max = current.data + end + 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(n) def find_min - raise NotImplementedError + if @head.nil? + return nil + end + current = @head + min = @head.data + until current.next.nil? + current = current.next + if current.data < min + min = current.data + end + end + return min 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 + if @head.nil? + return 0 + end + count = 1 + current = @head + until current.next.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 + if @head.nil? + return nil + end + current = @head + count = 0 + until count == index || current.next.nil? + current = current.next + count += 1 + 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(n) def visit - raise NotImplementedError + if @head.nil? + return nil + end + current = @head + until current.nil? + 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(n) def delete(value) - raise NotImplementedError + if @head.nil? + return nil + end + previous = @head + current = @head + until current.data == value || current.nil? + 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: O(n) + # Space Complexity: O(1) def reverse - raise NotImplementedError + if @head.nil? + return nil + end + current = @head + until current.nil? + new_previous = current.next + new_current = new_previous.next + new_previous.next = current + current = new_current end @@ -115,25 +192,45 @@ def has_cycle # 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 + if @head.nil? + return nil + else + return @head.data + end 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 + new_node = Node.new(value) + if @head.nil? + @head = new_node + else + current = @head + until current.next.nil? + current = current.next + end + current.next = new_node + end 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(1) + # Space Complexity: O(1) def get_last - raise NotImplementedError + if @head.nil? + return nil + end + current = @head + while current.next != nil + current = current.next + end + return current.data end # method to insert a new node with specific data value, assuming the linked @@ -158,4 +255,5 @@ def create_cycle current.next = @head # make the last node link to first node end + end end