Project Euler

Problem 6: Sum Square Difference

The sum of the squares of the first ten natural numbers is 1² + 2² + ... + 10² = 385. The square of the sum of the first ten natural numbers is (1 + 2 + ... + 10)² = 55² = 3025. Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 - 385 = 2640. Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.

The Catch

This problem is straight forward enough to efficiently brute force.

The Light

Loop from 1 to 100 and accumulate the sum of the squares and the sum for each iteration. After the loop is completed, find their difference.

The Code

public class Problem6
{
  public static void main(String[] args)
  {
    int s1 = 0;
    int s2 = 0;

    for(int i = 1; i <= 100; i++)
    {
      s1 += (i*i);
      s2 += i;
    }
    System.out.println(s2 * s2 - s1);
 }
}