← DSA Foundations
easyBasic Math Concepts

Check for Prime

Determine whether n is prime: it must be at least 2 and have exactly two positive divisors.

GeeksforGeeks ↗

Work through the cases

3 examples

Input notation

An integer n from 0 through 1000000000.

Expected result

true or false.
Case 1

Input

29

Expected output

true
Case 2

Input

1

Expected output

false
Case 3

Input

2

Expected output

true

These notes use simplified input/output notation. The linked platform defines the method signature and judge format.

FROM IDEA TO IMPLEMENTATION

Understand the approach.

Compare the documented approaches below. Brute force, better, and optimal versions appear where available; a direct exercise may need only one approach.

A composite number has a divisor no larger than its square root. Reject numbers below 2. Time: O(√n), extra space: O(1).

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        ArrayList<Long> values = new ArrayList<>();
        while (in.hasNextLong()) values.add(in.nextLong());
        long[] a = values.stream().mapToLong(Long::longValue).toArray();
        long n = a[0];
        boolean prime = n >= 2; for (long i = 2; i <= n / i; i++) if (n % i == 0) { prime = false; break; } System.out.println(prime);
    }
}

Reference code. Platform solutions may use supplied node types, imports, or collection libraries; foundational examples are complete programs.