# 236.LowestCommonAncestorofaBinaryTree
// https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree/
/**
* Definition for a binary tree node.
* function TreeNode(val) {
* this.val = val;
* this.left = this.right = null;
* }
*/
/**
* @param {TreeNode} root
* @param {TreeNode} p
* @param {TreeNode} q
* @return {TreeNode}
*/
var lowestCommonAncestor = function(root, p, q) {
if (!root) {
return null;
}
if (root === p || root === q) {
return root;
}
var left = lowestCommonAncestor(root.left, p, q);
var right = lowestCommonAncestor(root.right, p, q);
if (left && right) {
return root;
} else if (left) {
return left;
} else {
return right;
}
};