Question

我正在尝试追溯性地在Trie上构建测试。 trie实际上工作并返回存储的单词，但是当我尝试对哈希运行测试时，它告诉我Trie正在生成一个nilclass。

这是t9_trie.rb（调整以反映falsetru的v有用修复）

class Trie
  def initialize
    @root = Hash.new
  end

  def build(word) 
    node = @root
    t9num = word.tr('a-z', '22233344455566677778889999')
    t9num.each_char do |ch|
      node[ch] ||= Hash.new
      node = node[ch]
    end
    (node[:end] ||= []) << word
  end

  def find(str) 
    node = @root
    str.each_char do |ch|
      return nil unless node = node[ch]
    end
    node[:end] && true
    node[:end].to_a
  end
end

# words = %w[ant bear cat anu amulet quest question whatchamacalit yes zest]
# words = File.open('dictionary_copy.txt') {|f| f.read }.split

word = "ant"
t = Trie.new
t.build("#{word}")
puts t.inspect
puts t.find('268').class
search = [t.find('268')]
ary = search.to_a
puts ary.class
puts ary

这里是t9_trie_spec.rb，现在有效：

require 'test/unit'
here = File.expand_path(File.dirname(__FILE__))
require "#{here}/sandbox"

class StringExtensionTest < Test::Unit::TestCase

  def test_if_Trie_exists
    word = "ant"
    t = Trie.new
    t.build("#{word}")
    assert_match /Trie/, t.to_s, "no Trie found"
  end

  def test_if_find_works
    word = "ant"
    t = Trie.new
    t.build(word)
    search = t.find('268') #had to remove extra nested arrays
    assert_send([search, :member?, word]) #and tweak this language
  end

end

Answer 1

print的返回值为nil

irb(main):001:0> a = print '1'
1=> nil

您应该在print方法的最后一个语句中删除print（或将return替换为find）：

class Trie

  ...

  def find(str) 
    node = @root
    str.each_char do |ch|
      return nil unless node = node[ch]
    end
    node[:end] && true
    node[:end].to_a # <-------------- remove print
  end
end

更改了测试用例（也用`word替换了"#{word}"：

require 'test/unit'

class StringExtensionTest < Test::Unit::TestCase
  ...
  def test_if_find_works
    word = "ant"
    t = Trie.new
    t.build(word)
    search = t.find('268')
    ary = search.to_a
    assert(ary.member? word)
  end
end

试图在trie上运行测试，但它现在没有了，我看不出原因

1 个答案: