1261. 在受污染的二叉树中查找元素

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题目链接：1261. 在受污染的二叉树中查找元素

代码如下：

/*** 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 FindElements {
public:FindElements(TreeNode* root) {root->val=0;preorder(root);}bool find(int target) {if(arr.count(target))   return true;return false;}
private:unordered_set<int> arr;void preorder(TreeNode* root){if(root==nullptr)   return;arr.insert(root->val);if(root->left){root->left->val=2*root->val+1;preorder(root->left);}if(root->right)   {root->right->val=2*root->val+2;preorder(root->right);}}
};/*** Your FindElements object will be instantiated and called as such:* FindElements* obj = new FindElements(root);* bool param_1 = obj->find(target);*/