Replace Multiple Characters in string

Question

Hi all a have a program working but return string like ")Hi(" it should be "(Hi)" so i need to replace '(' with ')' and replace ')' with '(' it sounds easy

s.Replace('(',')').Replace(')','(')

the trick is that after the first replace the string change from ")Hi(" to "(Hi(" after the second the replace will change both characters back the final will become ")Hi)" Help Please

What if you have "(foo)Hi(bar)"? It should become ")foo(Hi)bar("? — Sergey Berezovskiy
– Sergey Berezovskiy, Commented May 13, 2017 at 9:14

LukStorms · Accepted Answer · 2017-05-13 10:50:32Z

2

You could also use a regex replacement.

s = System.Text.RegularExpressions.Regex.Replace(s, @"[)](\w+)[(]", "($1)");

answered May 13, 2017 at 10:50

LukStorms

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Comments

Steve · Accepted Answer · 2017-05-13 09:39:42Z

0

You cannot use Replace because it works its replacement operation on the whole string, not char by char.

A simple brute force solution could be this one

void Main()
{
    // A dictionary where every key points to its replacement char
    Dictionary<char, char> replacements = new Dictionary<char, char>()
    {
        {'(', ')'},
        {')', '('},
    };

    string source = ")Hi(";

    StringBuilder sb = new StringBuilder();
    foreach (char c in source)
    {
        char replacement = c;
        if(replacements.ContainsKey(c))
            replacement = replacements[c];
        sb.Append(replacement,1);

    }
    Console.WriteLine(sb.ToString());
}

You can transform this in an extension method adding to a static class

public static class StringExtensions
{
    public static string ProgressiveReplace(this string source, Dictionary<char, char> replacements)
    {
        StringBuilder sb = new StringBuilder();
        foreach (char c in source)
        {
            char replacement = c;
            if (replacements.ContainsKey(c))
                replacement = replacements[c];
            sb.Append(replacement, 1);
        }
        return sb.ToString();
    }
}

and call it from your code with

Dictionary<char, char> replacements = new Dictionary<char, char>() 
{{'(', ')'},{')', '('}};
s = s.ProgressiveReplace(replacements);

edited May 13, 2017 at 9:39

answered May 13, 2017 at 9:22

Steve

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4 Comments

Maher Khalil Over a year ago

thank you it worked but is there a way where i do it without looping the source string i'm working with articals and books looping will be bad

Steve Over a year ago

Somewhere someone should loop.

Slai Over a year ago

sounds like it will be a pretty big string, so I would recommend new StringBuilder(source.Length);

Steve Over a year ago

Yes that could be done but at the moment I have no clue on the actual length of the string

Alexander Petrov · Accepted Answer · 2017-05-13 09:57:39Z

0

var s = ")Hi(";            

var sb = new StringBuilder();

foreach (var c in s)
    if (c == ')')
        sb.Append('(');
    else if (c == '(')
        sb.Append(')');
    else
        sb.Append(c);

s = sb.ToString();

answered May 13, 2017 at 9:57

Alexander Petrov

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Comments

Deepak Tiwari · Accepted Answer · 2017-05-13 10:28:04Z

0

Method 1) Use the following:

var requiredString = string.Join(string.Empty, str.Select(x=>{if (x == '(') x = ')';  else if (x == ')') x = '('; return x;}));

Method 2) Or you can Use following Extension Method:

public static class StringExtensions
{
    public static string ReplaceMultiple(this string source, Dictionary<char, char> replacements)
    {
        return string.Join(string.Empty , source.Select(x=>Replace(x,replacements)));
    }

    private static char Replace(char arg, Dictionary<char, char> replacements)
    {
        if(replacements.ContainsKey(arg))
            arg = replacements[arg];
        return arg;
    }
}

This method can be used as follows:

        var rep = new Dictionary<char, char> 
        { 
            { ')', '(' }, 
            { '(', ')' }, 
            // { '#', '*' }, 
            // { '*', '#' } 
        };


        var c = str.ReplaceMultiple(rep);

edited May 13, 2017 at 10:28

answered May 13, 2017 at 9:48

Deepak Tiwari

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1 Comment

Slai Over a year ago

var s = string.Concat(")Hi(".Select(c => c == '(' ? ')' : c == ')' ? '(' : c)); but it will also be slow with big strings

Slai · Accepted Answer · 2017-05-13 10:49:55Z

0

Regex.Replace lets you process each Match (needs using System.Text.RegularExpressions;) :

string result = Regex.Replace(")Hi(", @"\(|\)", m => m.Value == "(" ? ")" : "(");

Alternative can be replacing one of the characters with something else:

string result = ")Hi(".Replace('(', '\0').Replace(')', '(').Replace('\0', ')');

edited May 13, 2017 at 10:49

answered May 13, 2017 at 10:39

Slai

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