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fix delete - #12
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cscott wants to merge 2 commits into
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fix delete#12cscott wants to merge 2 commits into
cscott wants to merge 2 commits into
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cscott
commented
Oct 15, 2026
cscott
commented
- fix: recompute the new subtree root max in rotateRight()
- fix: make deleteFixup() match CLRS RB-DELETE-FIXUP
After a right rotation the node that moved up ($x) must have its max recomputed, but the code recomputed $y a second time instead. The stale max on the new subtree root makes findIntersections() prune subtrees that do contain matches. Insert-only workloads mostly mask this because insert() re-walks the path to the root afterwards; the delete fix-up does not.
Two deviations from the textbook algorithm corrupted the tree on removal: * Case 2 must only apply when *both* of the sibling's children are black; the code tested only the near child. * After the case-3 rotation the sibling must be re-read from the parent (w = x.p.right / x.p.left); the code kept using the old sibling. Either one breaks the black-height or red-red invariant, after which later removals dereference the nil sentinel's (null) children and throw a TypeError, and queries return wrong results. Add a randomized test that checks findIntersections() and getSize() against a brute-force list across a mix of inserts and removals. On the previous code 45 of the 50 seeds fail.
Owner
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Thanks for the fixes! I went through both changes against CLRS and they look correct: the CI was failing for a reason unrelated to your changes: the workflow used the retired Could you rebase this branch onto the current |
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