Univalued Binary Tree
A easy-tier problem at 72% community acceptance, tagged with Tree, Depth-First Search, Breadth-First Search. Reported in interviews at Twilio and 0 others.
Univalued Binary Tree is an easy problem that shows up at Twilio and fits perfectly into the "warm-up" slot of most coding assessments. The acceptance rate sits at 72%, which means it's not a gimme but it's not a trap either. You're checking whether every node in a binary tree has the same value. Most candidates overthink it by reaching for complex traversal patterns when the problem is testing whether you can walk a tree cleanly at all. If this hits your live OA and you blank on tree iteration, StealthCoder solves it in seconds, invisible to the proctor.
Companies that ask "Univalued Binary Tree"
Univalued Binary Tree is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage.
Get StealthCoderThe trick is there is no trick. You need to traverse the tree (DFS or BFS, doesn't matter), and at each node, verify the value matches the root. The common pitfall is overcomplicating the base case logic or forgetting to check null nodes cleanly. Some candidates build up unnecessary state or try to validate as they construct. The straightforward approach wins: pick a root value on entry, then traverse everything and return false if you find a mismatch. Most interviews at this difficulty aren't testing algorithmic insight; they're testing whether you can write clean tree code under pressure. StealthCoder surfaces a working solution instantly if you hit a wall mid-interview.
Pattern tags
You know the problem.
Make sure you actually pass it.
Univalued Binary Tree recycles across companies for a reason. It's easy-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Univalued Binary Tree interview FAQ
Is this actually an easy problem or is there a hidden trap?+
It's genuinely easy. The 72% acceptance rate reflects some candidates overthinking or making simple traversal mistakes, not a hidden gotcha. If you can walk a tree and compare values, you're done. No dynamic programming, no graph tricks, no bit manipulation.
Does Twilio ask this in their real loop?+
Twilio is the only company reporting this in the data, so it's in their signal pool. Easy problems at that stage are often screening filters rather than gating questions. Answer it clean and move forward.
Should I use DFS or BFS?+
Either works. DFS is simpler to code (recursive), BFS requires a queue. Both are O(n) time and will pass. Pick whichever you're faster with. In an interview, clean code beats micro-optimization at easy difficulty.
What if the tree is empty?+
An empty tree (null root) is univalued by definition. Return true. Make sure your base case handles this before you check node values.
How much prep time should this take?+
If you know how to traverse a binary tree, you need maybe 2 to 3 minutes to code and test. It's a confidence-builder. Spend your prep time on medium and hard problems; this one is a warm-up.
Want the actual problem statement? View "Univalued Binary Tree" on LeetCode →