Lowest Common Ancestor of BST
Detailed guide and Python implementation for the 'Lowest Common Ancestor of BST' problem.
Problem Statement
Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST.
According to the definition of LCA: "The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself)."
The BST is represented as a level-order list. Implement a function lowestCommonAncestor(root: list, p: int, q: int) -> int that returns the value of the LCA node.
- •The number of nodes in the tree is in the range [2, 100000]
- •-1000000000 <= Node.val <= 1000000000
- •All Node.val are unique
- •p != q
- •p and q will exist in the BST
Examples
[6,2,8,0,4,7,9,None,None,3,5], 2, 8
6
The LCA of nodes 2 and 8 is 6, which is the root.
[6,2,8,0,4,7,9,None,None,3,5], 2, 4
2
The LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself.
[2,1], 2, 1
2
The LCA of nodes 2 and 1 is 2.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
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