二叉树篇

我觉得是比两个节点的深度，取min（一种情况）

 

DFS解题。

/*** Definition for a binary tree node.* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode(int x) { val = x; }* }*/
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) return right;if(right==null) return left;return root;}
}