linked1

gistfile1.rb

class LinkedListNode
  attr_accessor :value, :next_node
  def initialize(value, next_node=nil)
    @value = value
    @next_node = next_node
  end
end

def print_values(list_node)
  if list_node
    print "#{list_node.value} --> "
    print_values(list_node.next_node)
  else
    print "nil\n"
    return
  end
end

# 37
# 99, 37
# 12, 99

# 12, 99 # next_node = 99
# 12, nil # set next_node = prev_node which is nil
# prev_node = 12
# node = 99

# here we go again
# next_node = 37
# 99, 12 # set next_node = prev_node which is 12
# prev_node = 99
# node = 37

# here we go again
# next_node = nil
# 37, 99
# prev_node = 37
# node = nil

# while node wil not execute again
# We return 37. And this is how it would look like

# 12, nil
# 99, 12
# 37, 99

def reverse_list(node)
  prev_node = nil
  while node
    next_node = node.next_node
    node.next_node = prev_node

    prev_node = node
    node = next_node
  end
  prev_node
end

def reverse_list2(node)
  prev_node = nil
  while node
    next_node = node.next_node
    node.next_node = prev_node

    prev_node = node
    node = next_node
  end
  prev_node
end

class Stack
    attr_reader :data
    def initialize
        @data = nil
    end
    # Push a value onto the stack
    def push(value)
        @data = LinkedListNode.new(value, @data)
    end
    # Pop an item off the stack.
    # Remove the last item that was pushed onto the
    # stack and return the value to the user
    def pop
       @data = @data.next_node
    end

    def reverse
    end

    def print_nodes
      print_values(@data)
    end
end

node1 = LinkedListNode.new(37)
node2 = LinkedListNode.new(99, node1)
node3 = LinkedListNode.new(12, node2)

# stack = Stack.new
# stack.push(37)
# stack.push(99)
# stack.push(12)
#
# stack.print_nodes

print_values(node3)

puts "-------"

revlist = reverse_list(node3)

print_values(revlist)