Lowest Common Ancestor
Walk down while both values are on the same side. Where they split is the answer.
Decision · step 2 of 4BST Queries: Lowest common ancestor
Both 20 and 40 are smaller than 50, so both live to the left. Go left.
What you will see
Focus descends until the two targets part ways.
Cost
| Best | O(1) |
|---|---|
| Average | O(log n) |
| Worst | O(n) |
| Space | O(1) |
How you work with it here
play it through, step one change at a time, scrub to any step, run it on your own input, predict what happens next, try operations in any order.
Screen readers: Nodes announce value, left child and right child; each step announces the comparison and the direction taken or the structural change.
Reduced motion: Focus jumps node to node with a static ring; rotations become a crossfade between the two layouts.
Before this
Taught by the same lesson
BST Queries covers these too, in the same run.