/// <summary>
/// Try to parse header delimiter from numbers string.
/// </summary>
/// <param name="numbers">Numbers string.</param>
/// <param name="constraints">Constraint object.</param>
/// <returns></returns>
private static char[] TryGetDelimHeader(string numbers, DelimiterHeaderConstraints constraints)
{
// https://regex101.com/r/tXfHca/1
string delimHeaderMatchPattern = @$ "(?<={constraints.StartsWith}).*(?={constraints.EndsWith})";
var match = Regex.Match(numbers, delimHeaderMatchPattern);
if (match.Success)
{
return(match.Value.ToCharArray());
}
return(null);
}
/// <summary>
/// A simple string calculator which adds together specified numbers separated by commas. A custom
/// delimiter can be specified in the input before the number in the following way: //[delimiter]\n[numbers…]
/// </summary>
/// <param name="numbers">String input containing numbers and optional delimiter header.</param>
/// <returns>Sum of numbers.</returns>
public static int Add(string numbers)
{
// Default delimiter.
char[] delims = new[] { ',' };
// Default cases.
if (numbers == string.Empty)
{
return(0);
}
if (numbers == null)
{
throw new ArgumentNullException(nameof(numbers));
}
// Process header.
if (numbers.SafeSubstring(0, 2) == "//")
{
// We have the start of the delimiter header of our input, worth trying to parse at this stage.
// The assumption is made that a newline cannot be used as a delimiter.
var constraints = new DelimiterHeaderConstraints()
{
StartsWith = "//",
EndsWith = "\n"
};
var delimsFromHeader = TryGetDelimHeader(numbers, constraints);
if (delimsFromHeader != null)
{
if (delimsFromHeader.Contains('/'))
{
throw new ArgumentOutOfRangeException(nameof(numbers), "Invalid delimiter header specified: '/'");
}
// We have found delims, so lets cut off the header up to the first newline encountered located AFTER the user specified delims.
// This allows the input have any number of newlines after the delim header.
var indexOfLastDelim = numbers.IndexOf(delimsFromHeader.Last());
numbers = numbers.Substring(indexOfLastDelim + 1);
numbers = numbers.Substring(numbers.IndexOf('\n') + 1);
// Brief point 4a states the requirements to "change" the delimiter, so we overwrite the default delim instead of adding to it.
delims = delimsFromHeader;
}
}
// Process numbers.
var total = 0;
var negativeAudit = "";
foreach (var strNum in numbers.Split(delims))
{
bool hasNegative = false;
int?parseResult = int.TryParse(strNum, out var num) ? num : default(int?);
if (parseResult == null)
{
throw new ArgumentNullException(nameof(numbers), "Invalid characters specified.");
}
if (num >= 1000)
{
continue;
}
if (num < 0)
{
hasNegative = true;
negativeAudit += num + ",";
}
if (!hasNegative)
{
total += num;
}
}
if (!string.IsNullOrEmpty(negativeAudit))
{
throw new ArgumentOutOfRangeException(nameof(numbers), $"Negatives not allowed: {negativeAudit.TrimEnd(',')}");
}
return(total);
}
