# Find Elements in a Contaminated Binary Tree

Given a binary tree with the following rules:

1. `root.val == 0`
2. If `treeNode.val == x` and `treeNode.left != null`, then `treeNode.left.val == 2 * x + 1`
3. If `treeNode.val == x` and `treeNode.right != null`, then `treeNode.right.val == 2 * x + 2`

Now the binary tree is contaminated, which means all `treeNode.val` have been changed to `-1`.

You need to first recover the binary tree and then implement the `FindElements` class:

* `FindElements(TreeNode* root)` Initializes the object with a contamined binary tree, you need to recover it first.
* `bool find(int target)` Return if the `target` value exists in the recovered binary tree.

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/11/06/untitled-diagram-4-1.jpg)

```
Input
["FindElements","find","find"]
[[[-1,null,-1]],[1],[2]]
Output
[null,false,true]
Explanation
FindElements findElements = new FindElements([-1,null,-1]); 
findElements.find(1); // return False 
findElements.find(2); // return True 
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2019/11/06/untitled-diagram-4.jpg)

```
Input
["FindElements","find","find","find"]
[[[-1,-1,-1,-1,-1]],[1],[3],[5]]
Output
[null,true,true,false]
Explanation
FindElements findElements = new FindElements([-1,-1,-1,-1,-1]);
findElements.find(1); // return True
findElements.find(3); // return True
findElements.find(5); // return False
```

**Example 3:**

![](https://assets.leetcode.com/uploads/2019/11/07/untitled-diagram-4-1-1.jpg)

```
Input
["FindElements","find","find","find","find"]
[[[-1,null,-1,-1,null,-1]],[2],[3],[4],[5]]
Output
[null,true,false,false,true]
Explanation
FindElements findElements = new FindElements([-1,null,-1,-1,null,-1]);
findElements.find(2); // return True
findElements.find(3); // return False
findElements.find(4); // return False
findElements.find(5); // return True
```

**Constraints:**

* `TreeNode.val == -1`
* The height of the binary tree is less than or equal to `20`
* The total number of nodes is between `[1, 10^4]`
* Total calls of `find()` is between `[1, 10^4]`
* `0 <= target <= 10^6`

```java
class FindElements {
    TreeNode root;
    Set<Integer> set;

    public FindElements(TreeNode root) {
        this.root = root;
        set = new HashSet<>();
        fillTree(this.root, 0);
    }

    public void fillTree(TreeNode root, int val) {
        if (root == null)
            return;
        set.add(val);
        root.val = val;
        fillTree(root.left, 2 * val + 1);
        fillTree(root.right, 2 * val + 2);
    }

    public boolean find(int target) {
        return set.contains(target);
    }
}
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://mayanktyagi3111.gitbook.io/interview-prep/hashmap-and-hashset-and-sliding-window/untitled-6.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.