Dot Star Regular Expression Matching in Java

// Dot Star Regular Expression Matching in Java
//
// PURPOSE
// This small matcher supports whole-sequence matching with a wildcard token and repetition
// of the preceding token.
//
// METHOD
// Use a table of prefix matches. A star can omit its preceding token or consume another
// matching text token. A non-star token extends the previous diagonal.
//
// COMPLEXITY
// O(nm) time and O(nm) space. Only dot and star semantics are supported; this is not a full
// regex engine.
//
// CONTRACT
// Tokens >=0 are literal; -1 is dot and -2 is star in the pattern. Star must follow a
// literal or dot, never another star. Returns 1 or 0.
// 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 regex_match(int[] text, int[] pattern) {
        java.util.Objects.requireNonNull(text, "text");
        java.util.Objects.requireNonNull(pattern, "pattern");
        int n = text.length;
        int m = pattern.length;
        alg_require(((n >= 0) && (n <= 1000000)));
        alg_require(((m >= 0) && (m <= 1000000)));
        alg_require((pattern.length == m));
        alg_require((text.length == n));
        for (int alg_i = 0; alg_i < m; alg_i++) {
            alg_require((pattern[alg_i] >= Math.negateExact(2)));
            alg_require(((pattern[alg_i] != Math.negateExact(2)) || ((alg_i > 0) && (pattern[Math.subtractExact(alg_i, 1)] != Math.negateExact(2)))));
        }
        int[] dp = new int[alg_size(Math.multiplyExact(Math.addExact(n, 1), Math.addExact(m, 1)))];
        dp[0] = 1;
        int i = 0;
        int j = 2;
        while ((j <= m)) {
            if ((pattern[Math.subtractExact(j, 1)] == Math.negateExact(2))) {
                dp[j] = dp[Math.subtractExact(j, 2)];
            }
            j = Math.addExact(j, 1);
        }
        i = 1;
        while ((i <= n)) {
            j = 1;
            while ((j <= m)) {
                if ((pattern[Math.subtractExact(j, 1)] == Math.negateExact(2))) {
                    dp[Math.addExact(Math.multiplyExact(i, Math.addExact(m, 1)), j)] = dp[Math.subtractExact(Math.addExact(Math.multiplyExact(i, Math.addExact(m, 1)), j), 2)];
                    if (((pattern[Math.subtractExact(j, 2)] == Math.negateExact(1)) || (pattern[Math.subtractExact(j, 2)] == text[Math.subtractExact(i, 1)]))) {
                        dp[Math.addExact(Math.multiplyExact(i, Math.addExact(m, 1)), j)] = Math.max(dp[Math.addExact(Math.multiplyExact(i, Math.addExact(m, 1)), j)], dp[Math.addExact(Math.multiplyExact(Math.subtractExact(i, 1), Math.addExact(m, 1)), j)]);
                    }
                } else {
                    if (((pattern[Math.subtractExact(j, 1)] == Math.negateExact(1)) || (pattern[Math.subtractExact(j, 1)] == text[Math.subtractExact(i, 1)]))) {
                        dp[Math.addExact(Math.multiplyExact(i, Math.addExact(m, 1)), j)] = dp[Math.subtractExact(Math.addExact(Math.multiplyExact(Math.subtractExact(i, 1), Math.addExact(m, 1)), j), 1)];
                    }
                }
                j = Math.addExact(j, 1);
            }
            i = Math.addExact(i, 1);
        }
        return dp[Math.addExact(Math.multiplyExact(n, Math.addExact(m, 1)), m)];
    }

    public static void main(String[] args) {
        int[] text = new int[] {1, 1, 2};
        int[] pattern = new int[] {1, -2, 2};
        int result = regex_match(text, pattern);
        System.out.println(result);
    }
}