有两个不同大小的二进制树：T1有上百万的节点；T2有好几百的节点。请设计一种算法，，判定T2是否为T1的子树。
/** * Definition of TreeNode: * class TreeNode { * public: *int val; *TreeNode *left, *right; *TreeNode(int val) { *this->val = val; *this->left = this->right = NULL; *} * } */class Solution {public:/*** @param T1, T2: The roots of binary tree.* @return: True if T2 is a subtree of T1, or false.*/bool isSubtree(TreeNode *T1, TreeNode *T2) {bool result = false;if (T2 == nullptr) {return true;}if (T1 == nullptr) {return false;}// write your code hereif (T1->val == T2->val) {result = dp(T1,T2);}if (!result) {result = isSubtree(T1->left,T2);}if (!result) {result = isSubtree(T1->right,T2);}return result;}bool dp (TreeNode *T1, TreeNode *T2) {if (T1 != nullptr && T2!=nullptr && T1->val == T2->val) {return dp(T1->left,T2->left) && dp (T1->right,T2->right);}if (T1 == nullptr && T2 == nullptr) {return true;}return false;}};
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