Soluție HackerRank pentru Twins, subdomeniul Number Theory, în Java 8. Include cerința formatată, exemple, explicația pașilor și cod sursă.
- Problemă: Twins
- Domeniu: Number Theory
- Limbaj: Java 8
Challenge: Twins
Subdomeniu: Number Theory (number-theory)
Scor cont: 30.0 / 30
Submission status: Accepted
Submission score: 1.0
Submission ID: 464727843
Limbaj: java8
Link challenge: https://www.hackerrank.com/challenges/twins/problem
Cerință
Lia is fascinated by anything she considers to be a *twin*. She calls a pairs of positive integers, i and j, twins if:
* They are both prime. A [prime](https://en.wikipedia.org/wiki/Prime_number) number is an integer greater than 1 that has no positive divisors other than 1 and itself.
* Their absolute difference is exactly equal to 2 (i.e., |j - i| = 2).
Given an inclusive interval of integers from n to m, can you help Lia find the number of pairs of twins there are in the interval (i.e., [n, m])? Note that pairs (i, j) and (j, i) are considered to be the same pair.
Input Format
Two space-separated integers describing the respective values of n and m.
Output Format
Print a single integer denoting the number of pairs of twins.
Constraints
* 1 ≤ n ≤ m ≤ 10^9
* m - n ≤ 10^6
Cod sursă
import java.math.BigInteger;
import java.util.Scanner;
public class Solution {
public static void main(String[] args) {
final int[] d = { 2, 4, 0 };
try (final Scanner in = new Scanner(System.in)) {
final int n = in.nextInt() | 1;
final int m = in.nextInt();
int count = n <= 3 && 5 <= m ? 1 : 0;
final int odd1 = n + d[n % 3];
final int max = m % 2 == 0 ? m - 3 : m - 2;
for (int i = odd1; i <= max; i += 6) {
boolean p1 = BigInteger.valueOf(i).isProbablePrime(30);
boolean p2 = BigInteger.valueOf(i + 2).isProbablePrime(30);
if (p1 && p2) {
count++;
}
}
System.out.print(count);
}
}
}