Question

我正在努力推翻一个句子。我能够做到。但我不确定，如何在不改变特殊字符位置的情况下扭转这个词。我正在使用正则表达式但是只要它找到特殊字符就会停止反转这个词。

以下是代码：

Console.WriteLine("Enter:");
string w = Console.ReadLine();   
string rw = String.Empty;
String[] arr = w.Split(' ');
var regexItem = new Regex("^[a-zA-Z0-9]*$");
StringBuilder appendString = new StringBuilder();
for (int i = 0; i < arr.Length; i++)
{
    char[] chararray = arr[i].ToCharArray();
    for (int j = chararray.Length - 1; j >= 0; j--)
    {

     if (regexItem.IsMatch(rw))
{
    rw = appendString.Append(chararray[j]).ToString();
}
    }
    sb.Append(' ');
}              
Console.WriteLine(rw);
Console.ReadLine();

示例：输入

马歇尔！你好。

预期输出

llahsram！ 2009东海生日贺。

Answer 1

使用正则表达式和LINQ的基本解决方案。 Try it online

public static void Main()
{
    Console.WriteLine("Marshall! Hello.");
    Console.WriteLine(Reverse("Marshall! Hello."));
}

public static string Reverse(string source)
{
    // we split by groups to keep delimiters
    var parts = Regex.Split(source, @"([^a-zA-Z0-9])");
    // if we got a group of valid characters
    var results = parts.Select(x => x.All(char.IsLetterOrDigit)
            // we reverse it
            ? new string(x.Reverse().ToArray())
            // or we keep the delimiters as it
            : x);
    // then we concat all of them
    return string.Concat(results);
}

没有LINQ的相同解决方案。 Try it online

public static void Main()
{
    Console.WriteLine("Marshall! Hello.");
    Console.WriteLine(Reverse("Marshall! Hello."));

}

public static bool IsLettersOrDigits(string s)
{
    foreach (var c in s)
    {
        if (!char.IsLetterOrDigit(c))
        {
            return false;
        }
    }
    return true;
}

public static string Reverse(char[] s)
{
    Array.Reverse(s);
    return new string(s);
}


public static string Reverse(string source)
{
    var parts = Regex.Split(source, @"([^a-zA-Z0-9])");

    var results = new List<string>();
    foreach(var x in parts)
    {
        results.Add(IsLettersOrDigits(x)
                   ? Reverse(x.ToCharArray())
                   : x);
    }
    return string.Concat(results);
}

Answer 2

这是一个没有LINQ的解决方案。我不确定什么是特殊字符。

        string sentence = "Marshall! Hello.";
        List<string> words = sentence.Split(' ').ToList();
        List<string> reversedWords = new List<string>();

        foreach (string word in words)
        {
            char[] arr = new char[word.Length];

            for( int i=0; i<word.Length; i++)
            {
                if(!Char.IsLetterOrDigit((word[i])))
                {
                    for ( int x=0; x< i; x++)
                    {
                        arr[x] = arr[x + 1];
                    }
                    arr[i] = word[i];
                }
                else
                {
                    arr[word.Length - 1 - i] = word[i];
                }
            }

            reversedWords.Add(new string(arr));
        }

        string reversedSentence = string.Join(" ", reversedWords);

        Console.WriteLine(reversedSentence);

这是输出：

   Updated Output = llahsraM! olleH.

Answer 3

这是一个非正则版本，可以满足您的需求：

var sentence = "Hello, john!";
var parts = sentence.Split(' ');
var reversed = new StringBuilder();
var charPositions = sentence.Select((c, idx) => new { Char = c, Index = idx })
                            .Where(_ => !char.IsLetterOrDigit(_.Char));

for (int i = 0; i < parts.Length; i++)
{
     var chars = parts[i].ToCharArray();

     for (int j = chars.Length - 1; j >= 0; j--)
     {
         if (char.IsLetterOrDigit(chars[j]))
         {
            reversed.Append(chars[j]);
         }
     }
}

foreach (var ch in charPositions)
{
    reversed.Insert(ch.Index, ch.Char);
}

// olleH, nhoj!
Console.WriteLine(reversed.ToString());

基本上，技巧是记住特殊（即非字母或数字）字符的位置，并将它们插入到那些位置的末尾。

Answer 4

此解决方案没有LINQ和Regex。这可能不是一个有效的答案，但是对于较小的字符串值可以正常工作。

    // This will reverse the string and special characters will just stay there.
    public string ReverseString(string rString)
    {
        StringBuilder ss = new StringBuilder(rString);
        int y = 0;
        // The idea is to swap values. Like swapping first value with last one. It will keep swapping unless it reaches at the middle of the string where no swapping will be needed.
        // This first loop is to detect first values.
        for(int i=rString.Length-1;i>=0;i--)
        {
            // This condition is to check if the values is String or not. If it is not string then it is considered as special character which will just stay there at same old position.
            if(Char.IsLetter(Convert.ToChar(rString.Substring(i,1))))
            {          
                // This is second loop which is starting from end to swap values from end with first.         
                for (int k = y; k < rString.Length; k++)
                {
                    // Again checking last values if values are string or not. 
                    if (Char.IsLetter(Convert.ToChar(rString.Substring(k, 1))))
                    {
                        // This is swapping. So st1 is First value in that string
                        // st2 is the last item in that string
                        char st1 = Convert.ToChar(rString.Substring(k, 1));
                        char st2 = Convert.ToChar(rString.Substring(i, 1));

                        //This is swapping. So last item will go to first position and first item will go to last position, To make sure string is reversed.
                        // Remember when the string value is Special Character, swapping will move forward without swapping.
                        ss[rString.IndexOf(rString.Substring(i, 1))] = st1;
                        ss[rString.IndexOf(rString.Substring(k, 1))] = st2;
                        y++;
                        // When the swapping is done for first 2 items. The loop will stop to change the values.
                        break;
                    }
                    else
                    {
                        // This is just increment if value was Special character. 
                        y++;
                    }
                }                    
            }
        }

        return ss.ToString();
    }

谢谢！

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4 个答案: