I used Visual Studio 2012 and C# to implement following questions. For unit tests I used nUnit framework (to launch nUnit tests in Visual Studio you need to have nUnit test adapter or you can use ReSharper to launch them).

Given a string, write a routine that converts the string to a long, without using the built in functions that would do this. Describe what (if any) limitations the code has. For example:

long stringToLong(String s)
{
    /* code goes here to convert a string to a long */
}

void test()
{ 
    long i = stringToLong("123");
    if (i == 123)
        // success
    else
        // failure
}

Function stringToLong is implemented in file Parser.cs. Unit tests are implemented in ParserSuites.cs. Current implementation has several limitations:

1. Function cannot parse long values represented in HEX format, like 0x123 (unit test StringToLong_HexValue_ThrowsFormatException).
2. Function cannot parse long values in strings, which contain group separators, like 1,000,000 (unit test StringToLong_CultureSpecificInputValueWithGroupSeparators_ThrowsFormatException(.

Implement insert and delete in a tri-nary tree. A tri-nary tree is much like a binary tree but with three child nodes for each parent instead of two -- with the left node being values less than the parent, the right node values greater than the parent, and the middle nodes values equal to the parent.

For example, suppose I added the following nodes to the tree in this order: 5, 4, 9, 5, 7, 2, 2.

The resulting tree would look like this:

     5
   / | \
  4  5  9
 /     /
2    7
|
2

Tri-nary tree structure is implemented in file TrinaryTree.cs. Current implementation allows to use any value types as a structure values. Because all values are value types we can use one trick to store middle-node. On middle node you can store only values which are equal to parent node. That means that by middle-node direction we can have only values which are equal to parent node, so we do not need to store real nodes, we can just count what is the depth of middle nodes.

To store any C# types in current structure we will need to change couple places: a) add validations for null values, b) change how we store middle node, instead of simple counter we can use Stack for that.

Unit tests for TrinaryTree are implemented in TrinaryTreeSuites.cs. This class contains only two methods, but in fact it contains 13 unit tests. One of unit tests Remove_TestCase expects test cases, which we provide with source RemoveTestCaseSource (see documentation for TestCaseSourceAttribute)