LeetCode 100. Same Tree

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

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

Example 1:

Input:     1         1
          /        / 
         2   3     2   3

        [1,2,3],   [1,2,3]

Output: true

Example 2:

Input:     1         1
          /           
         2             2

        [1,2],     [1,null,2]

Output: false

Example 3:

<b>Input:</b>     1         1
          /        / 
         2   1     1   2

        [1,2,1],   [1,1,2]

<b>Output:</b> false

/**
 * Definition for a binary tree node.
 * 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) { //树的遍历
         if((p==NULL&&q!=NULL)||(p!=NULL&&q==NULL))
             return false;
         else if(p==NULL&&q==NULL)
             return true;
         else if(p->val!=q->val)
             return false;
         //if(p!=NULL&&q!=NULL){
            if(!isSameTree(p->left,  q->left))
                return false; 
            if(!isSameTree(p->right, q->right))
                return false;
        // }
         return true;
    }
};