Maximum Subtree of the Same Color
A medium-tier problem at 57% community acceptance, tagged with Array, Dynamic Programming, Tree. Reported in interviews at BlackRock and 0 others.
Maximum Subtree of the Same Color is a medium-difficulty tree problem that appears in BlackRock assessments. You're given a tree and need to find the largest subtree where all nodes share the same color. The catch: a naive recursive pass won't cut it if you're not careful about what counts as a valid subtree and how you're tracking state. Acceptance hovers around 57%, meaning half the candidates either miscalculate the subtree size or misunderstand the color constraint. If you hit this during a live assessment and blank on the DFS pattern, StealthCoder surfaces a working solution in seconds while you stay invisible to the proctor.
Companies that ask "Maximum Subtree of the Same Color"
Maximum Subtree of the Same Color 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 core pattern is post-order DFS with state propagation. You traverse the entire tree, and at each node you track whether the subtree rooted there has uniform color, plus the size if it does. The trick most people miss: a valid same-color subtree only exists if all children either confirm uniformity with the same color or are leaves. You can't just count nodes and hope; you need to explicitly validate that every path from root to leaf within the subtree respects the constraint. Common failure: checking only immediate children instead of propagating the color requirement down. The algorithm runs O(n) time and O(h) space (recursion stack). When you're grinding the problem beforehand, focus on the return signature (size, is_uniform, color) from each DFS call. If you haven't drilled this tree-DP pattern before live interview day, StealthCoder is your hedge to surface the correct approach when panic sets in.
Pattern tags
You know the problem.
Make sure you actually pass it.
Maximum Subtree of the Same Color 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 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.
Maximum Subtree of the Same Color interview FAQ
Is this problem still asked at BlackRock?+
Yes. It's the only company listed in assessment reports for this problem, appearing in their medium-difficulty tier. If you're interviewing there, this one's on the board.
What's the gotcha that kills candidates?+
Treating same-color subtree as 'all nodes in the subtree happen to be the same color' instead of 'all nodes in the subtree must have the same color AND that color matches the parent's expectation'. State tracking from parent to child is critical.
How does this relate to standard tree DP?+
It's a direct application of post-order DFS with memoized state. You compute properties bottom-up and bubble aggregate results to parents. Similar shape to balanced subtree or max-path-sum problems, but the color constraint adds a validation layer.
Can I solve this iteratively or is recursion mandatory?+
Recursion is the cleaner fit because you need to process all descendants before deciding if a node's subtree is valid. Iterative approaches with an explicit stack are possible but error-prone; most candidates stick with recursive DFS.
How much time should I spend on this before the OA?+
If tree DP is weak, spend 45 to 60 minutes drilling post-order traversal patterns and state-passing logic first. Then 30 minutes on this specific problem. Medium acceptance means it's a real stumbling block; don't skip it.
Want the actual problem statement? View "Maximum Subtree of the Same Color" on LeetCode →