ruby 在LinkedList上实现了insert_before / after

Posted 2021-05-16

require 'pp'

class LinkedList
  attr_accessor :head

  def initialize(head=nil)
    @head = head
  end

  def add_to_head(node)
    pp "add to head"
    node.nxt = @head
    @head = node
  end

  def add_to_tail(node)
    runner = @head
    while(runner.nxt)
      pp "runner #{runner} #{runner.nxt}"
      runner = runner.nxt
    end
    runner.nxt = node
  end

  def traverse
    runner = @head
    while(runner)
      pp "runner:#{runner} val:#{runner.val} nxt=#{runner.nxt}"
      runner = runner.nxt
    end
  end

  def delete_by_value(value)
    runner = @head
    count = 0
    while(runner)
      if runner.nxt && runner.nxt.val == value
        pp "delete #{runner.nxt}:#{runner.nxt.val}"
        runner.nxt = runner.nxt.nxt
        count += 1
      end
      runner = runner.nxt
    end
    count
  end

  def insert_after(node, value)
    runner = @head
    while(runner)
      break if runner.nil?
      if runner.val == value
        node.nxt = runner.nxt
        runner.nxt = node
      end
      runner = runner.nxt
    end
    self
  end

  def insert_before(node, value)
    runner = @head
    while(runner)
      break if runner.nil? || runner.nxt.nil?
      if runner.nxt.val == value
        node.nxt = runner.nxt
        runner.nxt = node
        runner = node
      end
      runner = runner.nxt
    end
    self
  end
end

class Node
  attr_accessor :val, :nxt

  def initialize(val="")
    @val = val
    @nxt = nil
  end
end