解法一：递归

1 bool isSameTree(TreeNode* p, TreeNode* q) 2 { 3     if (p == NULL && q == NULL) 4         return true; 5     if ((p == NULL && q != NULL) || (p != NULL && q == NULL)) 6         return false; 7     if (p->val != q->val) 8         return false; 9 10     if (!isSameTree(p->left, q->left) || !isSameTree(p->right, q->right))11         return false;12 13     return true;14 }

解法二：非递归

1 bool isSameTree(TreeNode* p, TreeNode* q) 2 { 3     queue
     
      
        > pq_queue; 4     pq_queue.push(make_pair(p, q)); 5  6     while (!pq_queue.empty()) { 7         TreeNode *pTmp = pq_queue.front().first; 8         TreeNode *qTmp = pq_queue.front().second; 9         pq_queue.pop();10 11         if (pTmp == NULL && qTmp == NULL)12             continue;13         if (pTmp == NULL || qTmp == NULL)14             return false;15         if (pTmp->val != qTmp->val)16             return false;17 18         pq_queue.push(make_pair(pTmp->left, qTmp->left));19         pq_queue.push(make_pair(pTmp->right, qTmp->right));20     }21     return true;22 }