Deep Merge of Two Objects
A medium-tier problem at 64% community acceptance, tagged with . Reported in interviews at Valve and 0 others.
Deep Merge of Two Objects shows up in your Valve assessment if they're testing whether you understand object recursion and reference handling. This problem sits at the intersection of data structure manipulation and real-world engineering: you're not just merging two flat objects, you're navigating nested structures without losing data or breaking references. At 64% acceptance, it's medium-tier but the gap between a surface solution and a bulletproof one is wider than most candidates expect. If you hit this live and freeze on the recursion pattern, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Deep Merge of Two Objects"
Deep Merge of Two Objects 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 StealthCoderThe trick here is recognizing that a naive shallow merge fails the moment your objects contain nested objects. You need to recursively descend into each level, merging values as you go, and handle edge cases like nulls, arrays, and conflicting types. The gotcha is that you can't just copy references: you need actual deep cloning at each step, or you'll corrupt the original objects or create shared state that breaks downstream. Most candidates write the first pass correctly but miss the defensive cloning part or trip on the base case logic. The pattern is straightforward once you see it, but the details compound. StealthCoder is the hedge for the one variation you didn't drill because you thought you nailed the concept.
You know the problem.
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Deep Merge of Two Objects recycles across companies for a reason. It's medium-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.
Deep Merge of Two Objects interview FAQ
Is Deep Merge still asked at companies like Valve?+
Yes. It appears in their assessment pipeline, especially for roles involving configuration systems, game data merging, or systems engineering. At 64% acceptance, it's a problem Valve uses to filter candidates who understand recursion and object semantics, not just syntax.
What's the difference between shallow and deep merge here?+
Shallow merge copies top-level keys only; nested objects remain shared references. Deep merge recurses into every level and creates independent copies. Valve expects you to handle nested objects without corrupting the originals, so a shallow solution fails most test cases.
What's the most common mistake?+
Forgetting to clone nested objects before merging them. Candidates often write a recursive function that correctly identifies nested structures but then assign references instead of copies, causing mutations to leak back into the source objects. The proctor catches this in a second test case.
Do I need to handle arrays differently than objects?+
Usually. Arrays inside objects pose a choice: do you merge them by index, concatenate them, or replace them. The problem statement matters here, but most assessments expect you to treat arrays as atomic values and replace them, not recurse into them like you would with plain objects.
How does this relate to system design or real work?+
Configuration merging is everywhere: environment overrides, user settings layered on defaults, game state patches. Understanding deep merge teaches you how to safely compose data without side effects, a pattern you'll use in production code and system design interviews.
Want the actual problem statement? View "Deep Merge of Two Objects" on LeetCode →