## Problem description

A binary tree is univalued if every node in the tree has the same value.

Return true if and only if the given tree is univalued.

## Intuition

We've got to visit all the nodes of this tree and make sure they're the same value. So I'm figuring I can accomplish this with depth-first search or breadth-first search. Either will get the job done.

I'll set the first root value as my value check, since it's easy to grab that to start.

Then I can implement DFS or BFS. At each node, I'll check if the value matches the root node's value. If it doesn't, I can return false. If it does, I'll keep on going with the algorithm.

If the algorithm completes and I haven't returned false, I'll return true.

Here's how I expressed that in JavaScript:

```
var isUnivalTree = function(root) {
let val = root.val;
let response = true;
dfs(root);
return response;
function dfs(node) {
if (node.val !== val) {
response = false;
return;
}
if (node.left) {
dfs(node.left);
}
if (node.right) {
dfs(node.right);
}
}
};
```

I chose DFS purely because it's been a few weeks since I last coded it up and wanted aother refresher. Also note I'm using hoisting on the function - so I can call `dfs()`

above where I've defined it. On my first submission I forgot to actually call it and failed. Classic.