思路

典型的递归解法，注意递归的结束条件

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        
            //同时为空
            if(p == null && q == null) 
                 return true;
        
            //p、q中有一个为空，一个不为空（  
            if(p == null || q == null) 
                 return false;
        
        
            return  p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right); 
        
        
    }
}