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fix: make recursive LCS memoization unambiguous and cache empty results - #2241
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Shubham-Padkonde wants to merge 1 commit into
Open
Shubham-Padkonde wants to merge 1 commit into
Shubham-Padkonde wants to merge 1 commit into
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The recursive LCS memo key concatenates input suffixes with
:, so different states collide when the strings contain colons. It also treats a cached empty subsequence as a miss, causing exponential repeated work for disjoint strings.Key states by suffix lengths and check for
undefinedexplicitly. Cache matching-character states too.('::a:a', 'aa:::')now returns:::instead ofaa.Fixes #2233.
Validation: both new regressions fail before the fix. The empty-result regression counts substring expansions instead of relying on wall-clock timing. All 178 suites / 589 tests and the full coverage check pass; the changed algorithm has 100% coverage.
npm run lintpasses.AI-assisted contribution.