**Introduction**

When it comes to tackling complex problems in computer science, Leetcode is the go-to platform for many of us. Today, we're going to dive into one such problem, Leetcode 1361, titled "Validate Binary Tree Nodes." Don't let the 'medium' difficulty label intimidate you – we're here to break it down, step by step.

**Prerequisites**

Before we embark on this coding adventure, let's ensure we're on the same page. To tackle Leetcode 1361, it's helpful to have a basic understanding of binary trees and how they work. If you're unfamiliar with the concept, don't worry – we'll provide a quick refresher.

**Understanding the Main Concept**

The task at hand is to validate a binary tree. A binary tree is a hierarchical data structure that consists of nodes connected by edges. Each node can have, at most, two child nodes, a left child and a right child. For a binary tree to be valid, it must meet specific criteria:

- There should be exactly one root node.
- Each node, except the root, should have exactly one parent.
- There should be no cycles (i.e., no loops) in the tree.
- The tree should be connected, meaning every node can be reached from the root node.

Now, let's translate these criteria into a coding problem.

**Explaining with an Example**

Let's take a simple example to illustrate this. Suppose we have the following tree:

```
0
/ \
2 3
/ \
1 4
```

In this case, node 0 is the root, and it has two children, 2 and 3. Node 2, in turn, has children 1 and 4. This tree satisfies all the criteria for a valid binary tree.

**Step-by-Step Example**

To validate whether a given set of nodes forms a binary tree, we can follow these steps:

- Initialize two arrays to keep track of parent and children for each node.
- Iterate through all nodes and their children.
- For each node, check if it has more than one parent. If so, it's not a valid binary tree.
- For each child, check if it has more than one parent. If so, it's not a valid binary tree either.
- Check if there is exactly one node with no parent; this should be the root.
- Ensure that the root node can reach all other nodes.

By following these steps, you can tackle Leetcode 1361: Validating Binary Tree Nodes and conquer the world of binary trees. Happy coding!

## Top comments (0)