LeetCode SameTree

/**
 * 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);
    }
};