string-calculator

Instructions

Step 1: Simple Calculator

Create a simple String calculator with a single method:

class StringCalculator {
    int Add(string numbers);
}

The method can take 1 or 2 comma-separated numbers, and will return their sum.

The method returns 0 when passed the empty string.

Example:

Add("") // 0
Add("4") // 4
Add("1,2") // 3

Start with the simplest test case of an empty string and move to 1 and two numbers.

Step 2: Arbitrary number size

Allow the Add method to handle an unknown amount of numbers.

Example:

Add("1,2,3,4,5,6,7,8,9") // 45

Step 3: Newline separator

Allow the Add method to recognise newlines as well as commas as separators. The two separator types can be used interchangeably.

NB: Focus on the happy path - since this is not production code, it's fine if the code crashes if it's given invalid input (e.g. "1,\n2").

Example:

Add("1\n2,3") // 6

Step 4: Custom separators

Optionally support custom separators. To change separator, the beginning of the string will contain a separate line that looks like this: “//\n”

Example:

Add("//;\n1;2") // 3

Note that all existing scenarios should still be supported.

Step 5: Disallow negatives

Calling Add with a negative number will throw an exception negatives not allowed, and the negative that was passed.

If there are multiple negatives, show all of them in the exception message.

Example:

Add("1,-2,-3") // error: negatives not allowed: -2 -3

Step 6: Ignore numbers bigger than 1000

Numbers bigger than 1000 should be ignored.

Example:

Add("1001, 2") // 2

Step 7: Arbitrary-length separators

Separators can be of any length if surrounded by square brackets.

Example:

Add("//[***]\n1***2***3") // 6

Step 8: Multiple single-length separators

Allow multiple single-character separators like this: “//[delim1][delim2]\n”

Example:

Add("//[*][%]\n1*2%3") // 6

Step 9: Multiple longer-length separators

Handle multiple separators with any character length.

Example:

Add("//[foo][bar]\n1foo2bar3") // 6