Solution to Project Euler Problem 28: Number spiral diagonals - Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows: 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?

• Java Code

package sikademy;
/**
 *
 * @author Archangel Macsika
 * Copyright (c) Sikademy. All rights reserved
 */


public class SikademyEulerSolution {

	private static final int SIZE = 1001;  // Must be odd

	public String run() {
		long sum = 1;  // Special case for size 1
		for (int n = 3; n <= SIZE; n += 2)
			sum += 4 * n * n - 6 * (n - 1);
		return Long.toString(sum);
	}

	public static void main(String[] args) {
                SikademyEulerSolution solution = new SikademyEulerSolution();
		System.out.println(solution.run());
	}	
}

• Python Code

# 
# @author Archangel Macsika
# Copyright (c) Sikademy. All rights reserved.
# 

def compute():
	SIZE = 1001  # Must be odd
	ans = 1  # Special case for size 1
	ans += sum(4 * i * i - 6 * (i - 1) for i in range(3, SIZE + 1, 2))
	return str(ans)


if __name__ == "__main__":
	print(compute())