How can I reverse string which contains spaces and special characters

Question

String reverse which contains spaces and special characters. How can I achieve this without using regex?

Input: "M @#.AD()/A?#M"

Output :"MADAM"

This seems like a very good use case for regular expressions - why don't you want to use them? — Diado, Jul 24 '19 at 09:30
First you need to remove the special characters from the string, check this : https://stackoverflow.com/questions/1120198/most-efficient-way-to-remove-special-characters-from-string. then reverse is, check this : https://stackoverflow.com/questions/228038/best-way-to-reverse-a-string — Hamza, Jul 24 '19 at 09:34
Welcome to Stack Overflow. Could you clarify the requirements? It doesn't look like this is string *reversal* - it's just filtering out certain characters. If you want reversal as well, I would separate the two steps - filter first, then reverse. — Jon Skeet, Jul 24 '19 at 09:37
As a side note: Using a palindrome for a reversing question is slightly confusing. — Freggar, Jul 24 '19 at 09:38

score 4 · Answer 1 · answered Jul 24 '19 at 09:44

4

Here's a one-liner:

string.Join("", input.Where(char.IsLetter).Reverse()));

answered Jul 24 '19 at 09:44

Thomas Ayoub

29,063
15
95
142

score 1 · Accepted Answer · edited Aug 02 '20 at 19:47

1

This code should work fine:

string n = "M @#.AD()/A?#M";
string tmp = Regex.Replace(n, "[^0-9a-zA-Z]+", "");

string backwards = new string(tmp.Reverse().ToArray());
Console.WriteLine(backwards);

Removing everything except the string(words).

"[^0-9a-zA-Z]+"

Here is the second version, but in my opinion you should use Regex for this case.

You can save the special characters in a string array and ask if they exist in the string with Contains.

Code:

string n = "M @#.AD()/A?#M";
string[] chars = new string[] {"?", " ", ",", ".", "/", "!", "@", "#", "$", "%", "^", "&", "*", "'", "\"", ";", "_", "(", ")", ":", "|", "[", "]" };
//Iterate the number of times based on the String array length.
for (int i = 0; i < chars.Length; i++)
{
      if (n.Contains(chars[i]))
      {
           n = n.Replace(chars[i], "");
      }
}
// To reverse the string
string backwards = new string(n.Reverse().ToArray());
Console.WriteLine(backwards);

edited Aug 02 '20 at 19:47

marc_s

732,580
175
1,330
1,459

answered Jul 24 '19 at 09:30

2

I thinkyou misinterpreted the question: `How can I achieve this without using regex?` – pappbence96 Jul 24 '19 at 09:31
There's no reason not to use a regex for this job. A very good answer actually. – Tanveer Badar Jul 24 '19 at 09:32
Yea sryy didn't see it, I'm going to edit it in 5min. – Jul 24 '19 at 09:32
Yes, This is also correct but I just have a special case where I won't use regex.It works for me.Thank You. – Vihar Jadhav Jul 24 '19 at 09:45

score 0 · Answer 3 · answered Jul 24 '19 at 09:37

One of the solutions that came to my mind:

    string input = "D @#.O()/?#G";

    StringBuilder builder = new StringBuilder();

    for (int i = input.Length-1; i >= 0; i--)
    {
        if (Char.IsLetter(input[i]))
        {
            builder.Append(input[i]);
        }
    }

    string result = builder.ToString();

Result is "GOD".

How can I reverse string which contains spaces and special characters

3 Answers3