diff --git a/lib/linked_list.rb b/lib/linked_list.rb index 0de1ee00..8e76194c 100644 --- a/lib/linked_list.rb +++ b/lib/linked_list.rb @@ -18,71 +18,145 @@ 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(1) + # Space Complexity: O(1) def search(value) - raise NotImplementedError + return false if @head.nil? + current = @head + + until current == nil + return true if current.data == value + 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 def find_max - raise NotImplementedError + return nil if @head.nil? + + max = @head.data + current = @head + + while current + max = current.data if current.data > max + 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 - end + return nil if @head.nil? + min = @head.data + current = @head + + while current + min = current.data if current.data < min + current = current.next + 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 + return 0 if @head.nil? + + count = 0 + current = @head + + 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 + index.times do + current = current.next + end + 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 + return nil if @head.nil? + + 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 + # return nil if @head.nil? + + current = @head + previous = nil + return nil if current.nil? + + until current.data == value + previous = current + current = current.next + end + + if previous.nil? + @head = current.next + else + previous.next = 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 + return nil if @head.nil? + + current = @head + previous = nil + + until current.next.nil? + temp = current.next + current.next = previous + previous = current + current = temp + end + current.next = previous + @head = current end @@ -118,7 +192,11 @@ def has_cycle # Time Complexity: ? # Space Complexity: ? 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