[Solved] How to split string by repeated characters? [closed]

by


Instead of splitting the string and then putting it back together again, you can just walk the string one character at a time, and build a result string from it. If you compare the current character with the previous character, you can determine whether or not to add a closing tag first, or just append the current character with the previous one (i.e. group “repeated” characters).

private static string GetOpeningSpan(char chr)
{
    // return an opening span with the correct color
    var validCharacters = new[] 
        {'F', 'L', 'R', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};

    if (!validCharacters.Contains(chr)) return "<span>";

    var color = chr == 'F' ? "pink" : chr == 'L' ? "red" : chr == 'R' ? "green" : "orange";

    return $"<span style=\"color: {color}\">";
}

private const string ClosingSpan = "</span>";

private static string GetHighlightedString(string input)
{
    if (string.IsNullOrWhiteSpace(input)) return input;

    // Add the opening span and first character
    var result = new StringBuilder().Append(GetOpeningSpan(input[0]) + input[0]);

    for (int i = 1; i < input.Length; i++)
    {
        var thisChar = input[i];
        var prevChar = input[i - 1];

        // If this character is the same as the previous one, just add it
        if (thisChar == prevChar || (char.IsDigit(thisChar) && char.IsDigit(prevChar)))
        {
            result.Append(thisChar);
        }
        else
        {
            // Add a closing span, and opnening span, and this character
            result.Append(ClosingSpan + GetOpeningSpan(thisChar) + thisChar);
        }
    }

    // Add a final closing span
    result.Append(ClosingSpan);

    return result.ToString();
}

solved How to split string by repeated characters? [closed]