Basic Problemscountingcombinatoricstree
Count Unique BSTs
Given n distinct keys, count how many structurally different binary search trees can be built using all of them. The BST property fixes each key's relative order; only the shape is free to vary.
Do this lesson first: climbing stairsThe full breakdown and animated table for this problem are still being written. In the meantime, run the four questions on it yourself — that is the whole exercise.