Question

我在Ruby中进行编程练习以确定字符串是否是回文结构。以下是我提出的建议：

dat %>%
  count(year, col2 = complete.cases(column2)) %>%
  ungroup() %>% 
  mutate(col2 = factor(col2, labels = c('unknown','known')))

返回以下内容：

# Write a method that takes a string and returns true if it is a
# palindrome. A palindrome is a string that is the same whether written
# backward or forward. Assume that there are no spaces; only lowercase
# letters will be given.
#
# Difficulty: easy.

def palindrome?(string)
    iterations=string.length/2
    is_palindrome=true
    i=0
    while i<iterations
        if string[i] != string[string.length-i-1]
            puts("string is not a palindrome")
            is_palindrome=false
        end
        i+=1
    end
    return is_palindrome 
end

# These are tests to check that your code is working. After writing
# your solution, they should all print true.

puts("\nTests for #palindrome?")
puts("===============================================")
    puts('palindrome?("abc") == false: ' + (palindrome?('abc') == false).to_s)
    puts('palindrome?("abcba") == true: ' + (palindrome?('abcba') == true).to_s)
    puts('palindrome?("z") == true: ' + (palindrome?('z') == true).to_s)
puts("===============================================")

第一个输出应该是＆＃34; false＆＃34;，我无法弄清楚为什么它没有返回。它打印＆＃34;字符串不是回文＆＃34;，所以我希望它也设置＆＃34; is_palindrome＆＃34;变量为＆＃34; false＆＃34;并返回。

Answer 1

就您的解决方案而言，我认为您错误地认为您的代码按预期工作。当然false == false是真的，所以palindrome?("abc') == false is true。

虽然与您的解决方案没有直接关系，但如何使用内置的reverse ruby功能

def palindrome?(string):
    string == string.reverse
end

Answer 2

免责声明：此答案无法解答您的问题，other answer更快。

如果你想测试你的代码，你也应该使用单元测试。

一个例子：

# Write a method that takes a string and returns true if it is a
# palindrome. A palindrome is a string that is the same whether written
# backward or forward. Assume that there are no spaces; only lowercase
# letters will be given.
#
# Difficulty: easy.

def palindrome?(string)
    iterations=string.length/2
    is_palindrome=true
    i=0
    while i<iterations
        if string[i] != string[string.length-i-1]
            #~ puts("string is not a palindrome")
            is_palindrome=false
        end
        i+=1
    end
    return is_palindrome 
end

# These are tests to check that your code is working. After writing
# your solution, they should all print true.
require 'minitest/autorun'
class FirstLetterTest < Minitest::Test
  def test_abc
    refute(palindrome?('abc'), "'abc' is detected as a palindrome, but it isn't")
  end
  def test_abcba
    assert(palindrome?('abcba'), "'abcba' is not detected as a palindrome")
  end
  def test_z
    assert(palindrome?('z'), "'z' is detected as a palindrome, but it isn't")
  end
end

我删除了您的puts("string is not a palindrome") - 它会混淆输出。

Ruby编程练习确定字符串是否是回文

2 个答案: