# ---
# title: 1361. Validate Binary Tree Nodes
# id: problem1361
# author: Tian Jun
# date: 2020-10-31
# difficulty: Medium
# categories: Graph
# link: <https://leetcode.com/problems/validate-binary-tree-nodes/description/>
# hidden: true
# ---
# 
# 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 <= 10^4`
#   * `leftChild.length == rightChild.length == n`
#   * `-1 <= leftChild[i], rightChild[i] <= n - 1`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
