String vs StringBuilder vs Span

Problem statement

During a recent interview, I was presented with a problem statement involving the use of the ’#’ symbol. The interviewer explained that this symbol should function as a backspace, and they requested me to devise a logical solution for resolving this scenario

Code

1: INPUT ==> abc#def# OUTPUT==> abcdef
2: INPUT ==> abc##def## OUTPUT==> ad

Solutions 1:

first Solution I write this,

  public string RemoveLastCharWithString(String word)
    {
        string result = "";
        for (int i = 0; i < word.Length; i++)
        {
            if (word[i] != ' ' && word[i] == '#')
            {
                result = result.Remove(result.Length - 1, 1);
            }
            else if (word[i] != '#')
            {
                result += word[i];
            }
        }
        return result;
    }

Solution 2:

I forced to be changed as stringbuilder

 public string RemoveLastCharWithStringBuilder(string word )
    {
        StringBuilder result = new StringBuilder();

        for (int i = 0; i < word.Length; i++)
        {
            if (word[i] != ' ' && word[i] == '#')
            { 
                if (result.Length > 0)
                {
                    result.Remove(result.Length - 1, 1);
                }
            }
            else if (word[i] != '#')
            {
                result.Append(word[i]);
            }
        }
        return result.ToString();
    }

Solution 3:

Then I realised we have other option and its optimized way to do .

   public string RemoveLastCharWithSpan(String word)
    {
        Span<char> buffer = stackalloc char[word.Length];
        int position = 0;

        foreach (char c in word)
        {
            if (c == '#' && position > 0)
            {
                position--;  
            }
            else if (c != '#')
            {
                buffer[position++] = c;  
            }
        }

        return new string(buffer.Slice(0, position));
    }

Benchmark Results

The metrix in below shows the results of our performance benchmarks.

Note: I will add separate article to show ” How to add BenchMarck in Dotnet ?”