Lowest Common Ancestor of a Binary Search Tree
Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes p and q in the BST.
According to the definition of LCA on Wikipedia: “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.”
Return the value of the LCA node.
Example 1
6
/ \
2 8
/ \ / \
0 4 7 9
/ \
3 5Input
root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 8Output
6The LCA of nodes 2 and 8 is 6.
Example 2
6
/ \
2 8
/ \ / \
0 4 7 9
/ \
3 5Input
root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 4Output
2The LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.
Constraints
- The number of nodes in the tree is in the range
[2, 10^5]. -10^9 <= Node.val <= 10^9- All
Node.valare unique. p != qpandqwill exist in the BST.