diff --git a/lib/linked_list.rb b/lib/linked_list.rb index 0de1ee00..ce5820bf 100644 --- a/lib/linked_list.rb +++ b/lib/linked_list.rb @@ -18,71 +18,180 @@ 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 + new_node.next = @head + end + + @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 + + return false if current.nil? && value != nil + + until current == nil + if current.data == value + return true + else + current = current.next + end + end + + return false # reached end of linked list, did not find 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 + current = @head + return nil if current.nil? + + max_val = current.data + + 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 + current = @head + return nil if current.nil? + + min_val = current.data + + until current == nil + + if current.data < min_val + min_val = current.data + end + + current = current.next + end + + return min_val 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 + current = @head + + return count if current.nil? + + until current == nil + count += 1 + current = current.next + 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 + return nil if @head.nil? + + current = @head + i = 0 + + until current == nil + if i == index + return current.data + else + i +=1 + current = current.next + end + end + + return nil # case when given index is larger than linked list size 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 + current = @head + return "empty linked list" if current.nil? + + until current == nil + puts 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 + # empty list case + return if @head.nil? + + # delete head case + if @head.data == value + @head = @head.next + return + end + + current = @head + + while current.next != nil + if current.next.data == value + current.next = current.next.next + return + end + + current = current.next + end + + return 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(n) def reverse - raise NotImplementedError + + # initialize + current = @head + previous = nil + + return if current.nil? + + while current != nil + temp = current.next + current.next = previous + previous = current + current = temp + end + @head = previous end @@ -158,4 +267,4 @@ def create_cycle current.next = @head # make the last node link to first node end -end +end \ No newline at end of file