Wednesday, September 17, 2014

Project Euler Solution using C#: Problem 28 : Number Spiral Diagonals

Problem:

Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows:

21 22 23 24 25
20 7 8 9 10
19 6 1 2 11
18 5 4 3 12
17 16 15 14 13

It can be verified that the sum of the numbers on the diagonals is 101.

What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed in the same way? My Solution:

static void Main(string[] args)
{
    static void Main(string[] args)
    {
        int limit = 1001 * 1001;
        int count = 0;
        int loopCount = 2;

        int sum = 1;   //1 coz the centervalue is 1. In loop counting from 3. 
        // every 4 iteration the increment count is adding +2
        for (int i = 3; i <= limit; i += loopCount)
        {
            sum += i;
            count += 1;
            if (count >= 4)
            {
                loopCount += 2;
                count = 0;
            }
        }
        Console.WriteLine(sum);
        Console.ReadLine();
    }
}

Note: You can simplifies the coding :)

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