Removes all but the first occurance of a given char in the string

June 28, 2022

I’m a beginner in C# and I’m stuck at this problem.

  string original = "foo bar foo $ bar $ foo bar $ ";  
  string desired_output = "foo bar foo $ bar foo bar";

I found a rough code but the result is not good.
can you help me solve the problem?

Here is my code:

  string s = "foo bar foo $ bar $ foo bar $ ";

  char ch = '$';

  for (int i = 0; i < s.Length; i++)
  {
      if (s[i] == ch)
      {
          s = s.Substring(0, i) +
          s.Substring(i + 1);
          break;
      }
   }
   
   for (int i = s.Length - 1; i > -1; i--)
   {            
       if (s[i] == ch)
       {
           s = s.Substring(0, i) +
           s.Substring(i + 1);
           break;
       }
   }
   Console.WriteLine(s);

The output I receive is foo bar foo bar $ foo bar.

>Solution :

string original = "foo bar foo $ bar $ foo bar $ "; 
string desired_output = "foo bar foo $ bar foo bar"; 

string result = original; 
int index = original.IndexOf("$")+1;    
if (index > 0) 
{
    result = (original.Substring(0, index)  + original.Substring(index).Replace("$", "")).Replace("  ", " ").Trim();
}

Console.WriteLine(desired_output == result);

See it here:

https://dotnetfiddle.net/I3lVua

Or:

string original = "foo bar foo $ bar $ foo bar $ "; 
string desired_output = "foo bar foo $ bar foo bar"; 

var buffer = original.ToCharArray();
bool found = false;
int dest = 0;
for(int i = 0; i < buffer.Length; i++)
{
    if (buffer[i] != '$' || !found)
    {
       buffer[dest] = buffer[i];
       dest++;
    }
    if (buffer[i] == '$') found = true;
}

var result = new string(buffer, 0, dest).Replace("  ", " ").Trim();
    
Console.WriteLine(desired_output == result);