Binary Tree Preorder Traversal
A easy-tier problem at 73% community acceptance, tagged with Stack, Tree, Depth-First Search. Reported in interviews at Yahoo and 1 others.
Binary Tree Preorder Traversal shows up in online assessments at Yahoo and Salesforce, and it looks deceptively simple. The acceptance rate sits at 73%, which means nearly 30% of people either time out, mess up the traversal order, or overthink a fundamentally straightforward problem. You've probably solved this in a DSA course and forgotten the exact sequence. If this problem hits your live OA and you blank on whether root comes first or last, StealthCoder surfaces a working solution in seconds while you stay invisible to the proctor.
Companies that ask "Binary Tree Preorder Traversal"
Binary Tree Preorder Traversal 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 at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share.
Get StealthCoderPreorder means visit the root, then left subtree, then right subtree. That's it. The trap is implementation: recursive is trivial, but iterative using a Stack requires you to remember the order you push children (right before left, so left pops first). Most people get the order wrong or mix up preorder with inorder or postorder under pressure. The topics here are Stack, Tree, Depth-First Search, and Binary Tree. You need to know both approaches cold because interviewers will ask you to do it iteratively if you go recursive first. If you hit this live and freeze on the stack pop order, StealthCoder runs invisibly and shows you the pattern so you can recover without breaking eye contact.
Pattern tags
You know the problem.
Make sure you actually pass it.
Binary Tree Preorder Traversal 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 at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Binary Tree Preorder Traversal interview FAQ
Is preorder traversal actually asked at FAANG-tier companies?+
Yahoo and Salesforce have reported asking it. It's a foundational tree pattern, so yes, you'll see it. The 73% acceptance rate means it's easier than median, but the 27% failure rate suggests people rush it. Treat it as mandatory baseline knowledge.
What's the trick everyone gets wrong?+
Stack order. When you push both children, push the right child first so the left child pops next. People reverse it under pressure. Also, people confuse preorder (root first) with inorder (left, root, right) or postorder (left, right, root). Lock down the sequence before the OA.
Recursive or iterative?+
Both. Recursive is two lines and obvious. Iterative using a Stack is the real test because it forces you to think about traversal order explicitly. Learn the iterative version and you own the concept. Recursive is your backup if you panic.
How does preorder relate to the other tree topics listed?+
Preorder is a specific Depth-First Search pattern using either recursion (implicit call stack) or an explicit Stack. Tree is the data structure. Stack is the tool for the iterative approach. Together they test whether you understand DFS at all, not just memorizing code.
How long should this problem take in a real OA?+
If you know it, under 5 minutes. If you're second-guessing yourself on order or mixing up traversal types, it balloons to 15-20. That's when the pressure kills you. Drill both solutions now so muscle memory carries you live.
Want the actual problem statement? View "Binary Tree Preorder Traversal" on LeetCode →