diff --git a/lib/linked_list.rb b/lib/linked_list.rb index 5e173ebc..2d3e038d 100644 --- a/lib/linked_list.rb +++ b/lib/linked_list.rb @@ -18,95 +18,186 @@ 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, @head) + @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) - Must traverse list + # Space Complexity: O(1) def search(value) - raise NotImplementedError + current = @head + while current + return true if value == current.data + current = current.next + 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) - Must traverse list + # Space Complexity: O(1) def find_max - raise NotImplementedError + current = @head + max = current&.data + while current + current = current.next + if current&.data && 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) - Must traverse list + # Space Complexity: O(1) def find_min - raise NotImplementedError - end + current = @head + min = current&.data + while current + current = current.next + if current&.data && current.data < min + min = current.data + end + 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 nil unless @head + return @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) - Must traverse list + # Space Complexity: O(1) def add_last(value) - raise NotImplementedError + current = @head + unless current + @head = Node.new(value) + return true + end + + while current&.next + current = current.next + end + + current.next = Node.new(value) end # method that returns the length of the singly linked list - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(n) - Must traverse list + # Space Complexity: O(1) def length - raise NotImplementedError + count = 0 + current = @head + while current + 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) - Must traverse list + # Space Complexity: O(1) def get_at_index(index) - raise NotImplementedError + count = 0 + current = @head + while current && count < index + 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) - Must traverse list + # Space Complexity: O(1) def visit - raise NotImplementedError + count = 0 + current = @head + while current && count < index + pp "Node #{count} is #{current.data}" + current = current.next + count += 1 + 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 + if @head&.data == value + @head = @head&.next + return true + end + + first = @head + second = first&.next + + while second + if second.data == value + first.next = second.next + return true + end + + first = first&.next + second = second.next + end + + return false 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 + first = nil + second = @head + + while second + third = second&.next + second.next = first + first = second + second = third + end + + @head = first + 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 + current = @head + while current.next + current = current.next + end + + return current&.data end ## Advanced Exercises