递归比较根，左节点， 右节点

/*** Definition for binary tree* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode(int x) { val = x; }* }*/
public class Solution {public boolean isSameTree(TreeNode p, TreeNode q) {if(p==null && q==null)return true;if(p==null || q==null)return false;if(p.val!=q.val)return false;return isSameTree(p.left,q.left)&&isSameTree(p.right,q.right);}
}