/** * 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) {        int v = ((p == NULL) << 1) + (q == NULL);        if (v == 0x2 || v == 0x1) return false; // one NULL the other not NULL        if (v == 0x3) return true;              // both NULL        if (p->val != q->val) return false;     // value not match        return isSameTree(p->left, q->left)     // check subtree                    && isSameTree(p->right, q->right);    }};