X Tutup
package ProjectEuler; /** * The sum of the squares of the first ten natural numbers is, * 1^2 + 2^2 + ... + 10^2 = 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 N natural * numbers and the square of the sum. *

* link: https://projecteuler.net/problem=6 */ public class Problem06 { public static void main(String[] args) { int[][] testNumbers = { {10, 2640}, {15, 13160}, {20, 41230}, {50, 1582700} }; for (int[] testNumber : testNumbers) { assert solution1(testNumber[0]) == testNumber[1] && solutions2(testNumber[0]) == testNumber[1]; } } private static int solution1(int n) { int sum1 = 0; int sum2 = 0; for (int i = 1; i <= n; ++i) { sum1 += i * i; sum2 += i; } return sum2 * sum2 - sum1; } private static int solutions2(int n) { int sumOfSquares = n * (n + 1) * (2 * n + 1) / 6; int squareOfSum = (int) Math.pow((n * (n + 1) / 2.0), 2); return squareOfSum - sumOfSquares; } }

X Tutup