A composite integer has a factor no larger than its square root.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 | // Trial Division Primality in Java // // PURPOSE // A composite integer has a factor no larger than its square root. Trial division checks // only candidate divisors up to that bound. // // METHOD // Reject values below two, handle two, and reject other even values. Test odd divisors until // d exceeds n/d, which avoids computing d squared. // // COMPLEXITY // O(sqrt(n)) time and O(1) auxiliary space. // // CONTRACT // Returns 1 for prime, 0 otherwise. This is suitable for small integers, not large // cryptographic candidates. // Public APIs infer array lengths except in C, which accepts pointer/length pairs. Vertex // counts and matrix dimensions remain explicit. Arrays must contain signed 32-bit integers. // Sorted order, correct tree topology, and caller-owned data-structure invariants are // preconditions; checking them on every query would change query complexity. // Scalar and shape checks are included. Value-range checks are included where needed to // prevent invalid indexing or nontermination. Allocation sizes are capped at 4,000,000 // workspace entries. Arithmetic outside Python raises an error on 32-bit overflow; Python // uses arbitrary precision. Native allocation failures propagate. In-place outputs may be // partly updated after arithmetic failure. These are single-threaded, in-memory // implementations. // // LANGUAGE DETAILS // Java 17+: primitive int arrays, Arrays.binarySearch for LIS, and Math exact arithmetic. // Invalid input throws IllegalArgumentException; arithmetic overflow throws // ArithmeticException. // // EXAMPLE // Expected return: 1. // Run: javac AlgorithmExample.java && java AlgorithmExample // Tests for this exact source artifact run before publication. The accompanying source // archive includes unit cases, runtime results, and source hashes. class AlgorithmExample { static void alg_require(boolean valid) { if (!valid) throw new IllegalArgumentException("invalid algorithm input"); } static int alg_size(int n) { alg_require(n>=0 && n<=4000000); return n; } static int is_prime(int n) { if ((n < 2)) { return 0; } if ((n == 2)) { return 1; } if (((n % 2) == 0)) { return 0; } int d = 3; while ((d <= (n / d))) { if (((n % d) == 0)) { return 0; } d = Math.addExact(d, 2); } return 1; } public static void main(String[] args) { int n = 97; int result = is_prime(n); System.out.println(result); } } |