Motivation

• Prevent process crashes and DoS caused by unchecked 32-bit multiplication and unvalidated CLI dimensions that could trigger NegativeArraySizeException, ArrayIndexOutOfBoundsException, or OutOfMemoryError when allocating the map or BFS queue.
• Avoid silent integer-parser overflow and malformed numeric tokens that can produce attacker-controlled dangerous dimensions.

Description

• Add a centralized validator checkedTotalCells(n, m) with a MAX_CELLS limit and use long multiplication to detect overflow and overly large maps, and throw IllegalArgumentException for invalid sizes.
• Use the validated total in solve and run, and check map.length consistency before allocating the BFS queue.
• Harden FastIn.nextInt() to reject non-digit characters and detect integer overflow while parsing, throwing IOException for invalid tokens.
• Wrap the CLI run() invocation in main with a try/catch that ignores IllegalArgumentException and IOException so invalid input is rejected gracefully without performing large allocations.

Testing

• Compiled the modified file with javac -d /tmp/classes src/main/java/algorithms/sprint6/WaterWorld.java and compilation succeeded.
• Verified correct behavior on valid input using printf '3 3\n#.#\n.#.\n#.#\n' | java -cp /tmp/classes algorithms.sprint6.WaterWorld which produced the expected output.
• Verified malicious inputs are rejected without crashing by running printf '50000 50000\n' | java -cp /tmp/classes algorithms.sprint6.WaterWorld and printf '2147483648 1\n' | java -cp /tmp/classes algorithms.sprint6.WaterWorld, both of which no longer trigger allocation crashes.
• Ran project tests with mvn test (initial run failed due to a transient Maven Central 502 Bad Gateway while resolving a dependency) and then retried mvn -q test, which completed (transient network failure noted).

Codex Task