/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
/*
func LCA
if root in (None, p, q) return root
left = LCA(root.left, p, q)
right = LCA(root.right, p, q)
return root if left and right else left or right
被发现的p或者q会被不断地向上传递，如果某个节点的左子树有p，右子树有q，则这个节点则为LCA
*/
public class Solution {
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
if (root == null || root == p || root == q) return root;
TreeNode left = lowestCommonAncestor(root.left, p, q);
TreeNode right = lowestCommonAncestor(root.right, p, q);
if(left != null && right != null) {
return root;
} else if (left != null){
return left;
} else if (right != null){
return right;
} else {
return null;
}
}
}