<p>You have <code>n</code> binary tree nodes numbered from <code>0</code> to <code>n - 1</code> where node <code>i</code> has two children <code>leftChild[i]</code> and <code>rightChild[i]</code>, return <code>true</code> if and only if <strong>all</strong> the given nodes form <strong>exactly one</strong> valid binary tree.</p> <p>If node <code>i</code> has no left child then <code>leftChild[i]</code> will equal <code>-1</code>, similarly for the right child.</p> <p>Note that the nodes have no values and that we only use the node numbers in this problem.</p> <p> </p> <p><strong class="example">Example 1:</strong></p> <img alt="" src="https://assets.leetcode.com/uploads/2019/08/23/1503_ex1.png" style="width: 195px; height: 287px;" /> <pre> <strong>Input:</strong> n = 4, leftChild = [1,-1,3,-1], rightChild = [2,-1,-1,-1] <strong>Output:</strong> true </pre> <p><strong class="example">Example 2:</strong></p> <img alt="" src="https://assets.leetcode.com/uploads/2019/08/23/1503_ex2.png" style="width: 183px; height: 272px;" /> <pre> <strong>Input:</strong> n = 4, leftChild = [1,-1,3,-1], rightChild = [2,3,-1,-1] <strong>Output:</strong> false </pre> <p><strong class="example">Example 3:</strong></p> <img alt="" src="https://assets.leetcode.com/uploads/2019/08/23/1503_ex3.png" style="width: 82px; height: 174px;" /> <pre> <strong>Input:</strong> n = 2, leftChild = [1,0], rightChild = [-1,-1] <strong>Output:</strong> false </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>n == leftChild.length == rightChild.length</code></li> <li><code>1 <= n <= 10<sup>4</sup></code></li> <li><code>-1 <= leftChild[i], rightChild[i] <= n - 1</code></li> </ul>