Lowest Common Ancestor of a Binary Tree
Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
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 lowest common ancestor of the nodes identified by p and q.
Example 1
3
/ \
5 1
/ \ / \
6 2 0 8
/ \
7 4Input
root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1Output
3The LCA of nodes 5 and 1 is 3.
Example 2
3
/ \
5 1
/ \ / \
6 2 0 8
/ \
7 4Input
root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4Output
5The LCA of nodes 5 and 4 is 5, 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 tree.