# 1361. Validate Binary Tree Nodes

https://leetcode.com/problems/validate-binary-tree-nodes

## Description

You have `n` binary tree nodes numbered from `0` to `n - 1` where node `i` has two children `leftChild[i]` and `rightChild[i]`, return `true` if and only if **all** the given nodes form **exactly one** valid binary tree.

If node `i` has no left child then `leftChild[i]` will equal `-1`, similarly for the right child.

Note that the nodes have no values and that we only use the node numbers in this problem.

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/08/23/1503_ex1.png)

```
**Input:** n = 4, leftChild = [1,-1,3,-1], rightChild = [2,-1,-1,-1]
**Output:** true
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2019/08/23/1503_ex2.png)

```
**Input:** n = 4, leftChild = [1,-1,3,-1], rightChild = [2,3,-1,-1]
**Output:** false
```

**Example 3:**

![](https://assets.leetcode.com/uploads/2019/08/23/1503_ex3.png)

```
**Input:** n = 2, leftChild = [1,0], rightChild = [-1,-1]
**Output:** false
```

**Example 4:**

![](https://assets.leetcode.com/uploads/2019/08/23/1503_ex4.png)

```
**Input:** n = 6, leftChild = [1,-1,-1,4,-1,-1], rightChild = [2,-1,-1,5,-1,-1]
**Output:** false
```

**Constraints:**

* `1 <= n <= 104`
* `leftChild.length == rightChild.length == n`
* `-1 <= leftChild[i], rightChild[i] <= n - 1`

## ac

```java
```
