diff --git a/lib/linked_list.rb b/lib/linked_list.rb index 0de1ee00..9945f85d 100644 --- a/lib/linked_list.rb +++ b/lib/linked_list.rb @@ -18,71 +18,158 @@ 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: o1 + # Space Complexity: o1 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: o1 + # Space Complexity: o1 def search(value) - raise NotImplementedError + current = @head + + while current + if current.data == value + return true + end + 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: on + # Space Complexity: o1 def find_max - raise NotImplementedError + return nil if @head == nil + + current = @head + max = @head.data + + while current + 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 = @head.data + + while current + if current.data < min + min = current.data + end + current = current.next + end + + return min end # method that returns the length of the singly linked list - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: on + # Space Complexity: o1 def length - raise NotImplementedError + current = @head + count = 0 + + while 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: on + # Space Complexity: o1 def get_at_index(index) - raise NotImplementedError + current = @head + count = 0 + + until current.nil? + return current.data if count == index + current = current.next + count += 1 + end + + return nil end # method to print all the values in the linked list # Time Complexity: ? # Space Complexity: ? def visit - raise NotImplementedError + print @head.data if @head.next == 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: on + # Space Complexity: o1 def delete(value) - raise NotImplementedError + return nil if @head.nil? + + if @head.data == value + @head = @head.next + return + end + + previous = @head + current = @head.next + + until current.nil? || current.data == value + 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: on + # Space Complexity: o1 def reverse - raise NotImplementedError + return nil if @head == nil + + current = @head + subsequent = nil + previous = nil + + while current + subsequent = current.next + current.next = previous + previous = current + current = subsequent + end + + @head = previous end @@ -91,7 +178,9 @@ def reverse # Time Complexity: ? # Space Complexity: ? def find_middle_value - raise NotImplementedError + length = self.length + mid = length/2 + return get_at_index(mid) end # find the nth node from the end and return its value @@ -118,14 +207,24 @@ 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 # Time Complexity: ? # Space Complexity: ? def add_last(value) - raise NotImplementedError + return nil if @head == nil + + current = @head + + return self.add_first(data) if current == nil + while current.next != nil + current = current.next + end + + current.next = Node.new(value) end # method that returns the value of the last node in the linked list @@ -133,6 +232,13 @@ def add_last(value) # Time Complexity: ? # Space Complexity: ? def get_last + current = @head + + while current.next != nil + current = current.next + end + + return current.data raise NotImplementedError end