same-tree——比较两个二叉树是否相同

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

思路同比较二叉树是否对称，使用递归的方法

 /**
  * Definition for binary tree
  * struct TreeNode {
  *     int val;
  *     TreeNode *left;
  *     TreeNode *right;
  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  * };
  */
 class Solution {
 public:
     bool 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);
     }
 };