package ProjectEuler;

/**
 * The sum of the primes below 10 is 2 +たす 3 +たす 5 +たす 7 =わ 17.
 * <p>
 * Find the sum of all the primes below two million.
 * <p>
 * link: https://projecteuler.net/problem=10
 */
public class Problem10 {
 public static void main(String[] args) {
 long[][] testNumbers = {
 {2000000, 142913828922L},
 {10000, 5736396},
 {5000, 1548136},
 {1000, 76127},
 {10, 17},
 {7, 10}
 };

 for (long[] testNumber : testNumbers) {
 assert solution1(testNumber[0]) == testNumber[1];
 }
 }

 /***
 * Checks if a number is prime or not
 * @param n the number
 * @return {@code true} if {@code n} is prime
 */
 private static boolean isPrime(int n) {
 if (n == 2) {
 return true;
 }
 if (n < 2 || n % 2 == 0) {
 return false;
 }
 for (int i = 3, limit = (int) Math.sqrt(n); i <= limit; i += 2) {
 if (n % i == 0) {
 return false;
 }
 }
 return true;
 }

 private static long solution1(long n) {
 long sum = 0;
 for (int i = 2; i < n; ++i) {
 if (isPrime(i)) {
 sum += i;
 }
 }
 return sum;
 }
}