Question:
I have a string read from another source such as "\b\bfoo\bx". In this case, it would translate to the word "fox" as the first 2 \b's are ignored, and the last 'o' is erased, and then replaced with 'x'. Also another case would be "patt\b\b\b\b\b\b\b\b\b\bfoo" should be translated to "foo"
I have come up with something using String.Replace, but it is complex and I am worried it is not working correctly, also it is creating a lot of new string objects which I would like to avoid.
Any ideas?
Solution:1
Probably the easiest is to just iterate over the entire string. Given your inputs, the following code does the trick in 1-pass
public string ReplaceBackspace(string hasBackspace) { if( string.IsNullOrEmpty(hasBackspace) ) return hasBackspace; StringBuilder result = new StringBuilder(hasBackspace.Length); foreach (char c in hasBackspace) { if (c == '\b') { if (result.Length > 0) result.Length--; } else { result.Append(c); } } return result.ToString(); }
Solution:2
The way I would do it is low-tech, but easy to understand.
Create a stack of characters. Then iterate through the string from beginning to end. If the character is a normal character (non-slash), push it onto the stack. If it is a slash, and the next character is a 'b', pop the top of the stack. If the stack is empty, ignore it.
At the end, pop each character in turn, add it to a StringBuilder, and reverse the result.
Solution:3
Regular expressions version:
var data = @"patt\b\b\b\b\b\b\b\b\b\bfoo"; var regex = new Regex(@"(^|[^\\b])\\b"); while (regex.IsMatch(data)) { data = regex.Replace(data, ""); } Optimized version (and this one works with backspace '\b' and not with string "\b"):
var data = "patt\b\b\b\b\b\b\b\b\b\bfoo"; var regex = new Regex(@"[^\x08]\x08", RegexOptions.Compiled); while (data.Contains('\b')) { data = regex.Replace(data.TrimStart('\b'), ""); }
Solution:4
public static string ProcessBackspaces(string source) { char[] buffer = new char[source.Length]; int idx = 0; foreach (char c in source) { if (c != '\b') { buffer[idx] = c; idx++; } else if (idx > 0) { idx--; } } return new string(buffer, 0, idx); } EDIT
I've done a quick, rough benchmark of the code posted in answers so far (processing the two example strings from the question, one million times each):
ANSWER | TIME (ms) ------------------------|----------- Luke (this one) | 318 Alexander Taran | 567 Robert Paulson | 683 Markus Nigbur | 2100 Kamarey (new version) | 7075 Kamarey (old version) | 30902
Solution:5
You could iterate through the string backward, making a character array as you go. Every time you hit a backspace, increment a counter, and every time you hit a normal character, skip it if your counter is non-zero and decrement the counter.
I'm not sure what the best C# data structure is to manage this and then be able to get the string in the right order afterward quickly. StringBuilder has an Insert method but I don't know if it will be performant to keep inserting characters at the start or not. You could put the characters in a stack and hit ToArray() at the end -- that might or might not be faster.
Solution:6
String myString = "patt\b\b\b\b\b\b\b\b\b\bfoo"; List<char> chars = myString.ToCharArray().ToList(); int delCount = 0; for (int i = chars.Count -1; i >= 0; i--) { if (chars[i] == '\b') { delCount++; chars.RemoveAt(i); } else { if (delCount > 0 && chars[i] != null) { chars.RemoveAt(i); delCount--; } } }
Solution:7
i'd go like this: code is not tested
char[] result = new char[input.Length()]; int r =0; for (i=0; i<input.Length(); i++){ if (input[i] == '\b' && r>0) r--; else result[r]=input[i]; } string resultsring = result.take(r);
Solution:8
Create a StringBuilder and copy over everything but backspace chars.
Note:If u also have question or solution just comment us below or mail us on toontricks1994@gmail.com
EmoticonEmoticon