Handle empty input in Distances

[krotname]

Motivation

• Fix a regression where Distances.solve() crashed with ArrayIndexOutOfBoundsException for an empty input array (n == 0) due to the sentinel-based backward scan starting at index 0.

Description

• Return the empty dist early in Distances.solve() with if (n == 0) return dist; and add an empty-array assertion assertEq(new int[]{}, solve(new int[]{}), "empty"); to the class's built-in tests in src/main/java/algorithms/sprint1/Distances.java to prevent the regression while preserving existing logic.

Testing

• Ran the full test suite with mvn test (all tests passed: 597 tests, build SUCCESS) and executed the class-level test() check via java -Dos.name=Windows -cp target/classes algorithms.sprint1.Distances which printed OK.

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Codex Task

[krotname]

Superseded by the validated combined merge in #115: #115