Java/ProjectEuler/Problem01.java at master · oribach/Java · GitHub

History

51 lines (43 loc) · 1.06 KB

Raw

package ProjectEuler;

/**

* If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9.

* The sum of these multiples is 23.

* <p>Find the sum of all the multiples of 3 or 5 below 1000.

* <p>Link: https://projecteuler.net/problem=1

public class Problem01 {

public static void main(String[] args) {

int[][] testNumber = {

{3, 0},

{4, 3},

{10, 23},

{1000, 233168},

{-1, 0}

};

for (int[] ints : testNumber) {

assert solution1(ints[0]) == ints[1];

assert solution2(ints[0]) == ints[1];

}

private static int solution1(int n) {

int sum = 0;

for (int i = 3; i < n; ++i) {

if (i % 3 == 0 || i % 5 == 0) {

sum += i;

}

return sum;

}

private static int solution2(int n) {

int sum = 0;

int terms = (n - 1) / 3;

sum += terms * (6 + (terms - 1) * 3) / 2;

terms = (n - 1) / 5;

sum += terms * (10 + (terms - 1) * 5) / 2;

terms = (n - 1) / 15;

sum -= terms * (30 + (terms - 1) * 15) / 2;

return sum;

}

Java/ProjectEuler/Problem01.java at master · oribach/Java · GitHub

Expand file tree

Breadcrumbs

Problem01.java

Latest commit

History

Breadcrumbs

Problem01.java

File metadata and controls