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Java-based LeetCode algorithm problem solutions, regularly updated
1361\. Validate Binary Tree Nodes
Medium
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
**Constraints:**
* `n == leftChild.length == rightChild.length`
* 1 <= n <= 104
* `-1 <= leftChild[i], rightChild[i] <= n - 1`