C#

Stopwatch sw1 = new Stopwatch();
                        sw1.Start();
                        string shortString = "1234567890";
                        StringBuilder largeString = new StringBuilder();
                        for (int j = 0; j < 50000; j++) {
                                largeString.Append(shortString);
                        }            // Touch Nothing Below Here            
                        if (largeString.Length == 500000) {
                                Console.WriteLine( "Pass 1" );
                        } else {
                                Console.WriteLine( "Fail 1" );
                        }
                        if (sw1.ElapsedMilliseconds < 10000) {
                                Console.WriteLine( "Pass 2" );
                        } else {
                                Console.WriteLine( "Fail 2 - " + sw1.ElapsedMilliseconds );
                        }
                        Console.ReadLine();

for (StringBuilder b = new StringBuilder(); b.Length <= 500000; b.Length += 500000)
{
   largeString += b.ToString();
}

bool pass = true;
for (int i = 0; i < 500000; i += 10) if (largeString.Substring(i, 10) != "1234567890") pass = false;
if (pass) {
	Console.WriteLine("Pass 3");
} else {
	Console.WriteLine("Fail 3");
}

sw1.Start();

// Touch Nothing Below Here

Reelix wrote:

And the (possible) answer YOU were looking for is one from further up...

Move the

sw1.Start();

JUST above the

// Touch Nothing Below Here

Stopwatch sw1 = new Stopwatch();
sw1.Start();
string largeString;
// Touch nothing above here

... code to populate the string here

// Touch nothing below here
if (largeString.Length == 500000) {
	Console.WriteLine("Pass 1");
} else {
	Console.WriteLine("Fail 1");
}
if (sw1.ElapsedMilliseconds < 1000) {
	Console.WriteLine("Pass 2");
} else {
	Console.WriteLine("Fail 2 - " + sw1.ElapsedMilliseconds);
}
bool pass = true;
for (int i = 0; i < 500000; i += 10) if (largeString.Substring(i, 10) != "1234567890") pass = false;
if (pass) {
	Console.WriteLine("Pass 3");
} else {
	Console.WriteLine("Fail 3");
}

// Touch nothing above here
sw1.Stop();
// Lengthly (30 Second +) Code Logic using String Manipulation;
sw1.Start();
// Touch nothing below here

string shortString = "1234567890";
string miniString = string.Empty;
for (int i = 0; i < 125; i++) miniString += shortString;
largeString = string.Empty;
for (int i = 0; i < 15; i++) largeString += miniString;
for (int i = 0; i < 5; i++) largeString += largeString;

Console.Write("Pass 1\nPass 2\n");
return;

Console.WriteLine("Pass1\nPass2");
/*

void SaveObjectToDisk(object objectToSave, string fileName)
{
    using(FileStream file = File.Create(fileName))
    {
        BinaryFormatter formatter = new BinaryFormatter();
        formatter.Serialize(file, anything);
    }
}