Split Concatenated Strings
A medium-tier problem at 43% community acceptance, tagged with Array, String, Greedy. Reported in interviews at Alibaba and 0 others.
Split Concatenated Strings is a medium-difficulty problem that shows up in Alibaba interviews and catches most candidates off guard. The acceptance rate sits at 43%, which means nearly six in ten people who attempt it walk away empty-handed. The trap is that the greedy solution feels right until you hit a test case where it fails silently. You either know the pattern or you don't, and if you hit this live and blank on the trick, StealthCoder solves it invisible to the proctor while you stay calm.
Companies that ask "Split Concatenated Strings"
Split Concatenated Strings 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 Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code.
Get StealthCoderThe problem asks you to split a concatenated string using a dictionary, and the greedy approach (always take the shortest or longest match first) will feel intuitive but fail on ambiguous splits. The real solution involves backtracking or dynamic programming to explore all valid split paths and pick the one that works. Common failure: candidates code a greedy scan, pass a few examples, then fail on inputs where early greedy choices block later valid splits. Arrays and string manipulation are table stakes; the Greedy topic is a red herring meant to make you commit to the wrong direction. If you haven't drilled backtracking on string partition problems, this is exactly where StealthCoder becomes your safety net during the live assessment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Split Concatenated Strings 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 Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Split Concatenated Strings interview FAQ
Why does the greedy approach fail here?+
Greedy assumes picking one match (shortest, longest, or first-found) leads to a valid split. But in Split Concatenated Strings, an early greedy choice can consume characters that would've matched a later valid dictionary word, leaving the remaining substring unsplittable. You need backtracking to try all paths.
Is this still asked at Alibaba?+
Yes. Alibaba's OA includes this problem and variants. The 43% acceptance rate reflects its real difficulty in the interview setting. Most candidates see it for the first time during the assessment, so preparation matters.
What's the core algorithmic pattern?+
Backtracking with memoization. Recursively try every dictionary word that matches the current position. If a path leads to a complete split, return true. If not, backtrack and try the next word. Cache results to avoid re-solving subproblems.
How does this relate to word break problems?+
This is a direct variant of the classic word-break DP problem. Both require you to determine if a string can be segmented into valid dictionary entries. Here, the constraint is stricter: you must split the entire input and sometimes reconstruct the path, not just return yes/no.
What's the time complexity trap?+
A naive backtracking solution without memoization can hit exponential time on large strings with many overlapping subproblems. Adding a memo dictionary cuts it to O(n^2) or O(n^3) depending on dictionary size. Miss the memo step and you'll TLE.
Want the actual problem statement? View "Split Concatenated Strings" on LeetCode →