题目链接：https://leetcode-cn.com/problems/subtree-of-another-tree/
题目如下：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isSubtree(TreeNode* root, TreeNode* subRoot) {
        //遍历完s，还没匹配到，则返回false
        if(root==NULL) return false;

        //短路运算符，有一个为真，则返回真
        return dfs(root,subRoot)||isSubtree(root->left,subRoot)||isSubtree(root->right,subRoot);
    }

    //此函数为判断两个子树是否相同的函数，同力扣第100题
    bool dfs(TreeNode* p1,TreeNode* p2){
        if(p1==NULL&&p2==NULL) return true;

        if(p1==NULL&&p2!=NULL) return false;
        if(p1!=NULL&&p2==NULL) return false;

        if(p1->val!=p2->val) return false;

        return dfs(p1->left,p2->left)&&dfs(p1->right,p2->right);
    }
};