Longest String Chain
A medium-tier problem at 62% community acceptance, tagged with Array, Hash Table, Two Pointers. Reported in interviews at Moloco and 8 others.
Longest String Chain shows up in assessments at Moloco, Two Sigma, Verily, Wix, Citadel, and five other serious shops. You're given a list of words and need to find the longest chain where each word is formed by adding exactly one letter to the previous word. The trick isn't obvious: naive recursion will time out. Most candidates either miss the DP angle or waste time on the wrong sorting strategy. If this problem lands in your live assessment and you freeze, StealthCoder surfaces a working solution invisible to the proctor.
Companies that ask "Longest String Chain"
Longest String Chain 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 pattern is sorting by word length, then using dynamic programming or hash tables to track the longest chain ending at each word. Many candidates think they need to brute-force all permutations or compare every pair of words, which fails at scale. The real move is recognizing that if a word can extend a previous chain, it can only extend chains from words exactly one character shorter. Build a hash table of word lengths, iterate in length order, and for each word test all possible single-character deletions to find predecessor chains. This reduces complexity dramatically. The acceptance rate sits at 62 percent, meaning solid preparation on Array, Hash Table, and Dynamic Programming patterns pays off. StealthCoder is your hedge if the DP state transitions don't click in the moment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Longest String Chain 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.
Longest String Chain interview FAQ
Is this still asked at big tech companies?+
Yes. The input data shows it's asked at nine significant firms including Two Sigma, Citadel, and Atlassian. These are the kind of shops that test harder DP problems. If you're interviewing at any FAANG-adjacent finance or infrastructure company, string chain problems are in the pool.
What's the actual trick most candidates miss?+
Sorting by word length first, then using a hash table of chains indexed by word. Candidates often try to compare every word pair or use recursion without memoization. Once you realize predecessors are always exactly one character shorter, the solution becomes linear in total characters. That insight separates accepted from rejected.
How does this relate to the DP topic?+
It's classic DP state reuse. The longest chain ending at word X depends on the longest chain ending at all valid predecessor words. You build up solutions from shorter words to longer words, storing the chain length at each word. Standard DP bottom-up without the 2D grid.
Will Hash Table and Two Pointers really come up in the solution?+
Hash Table absolutely. Two Pointers is optional. You hash words to track chains. Two Pointers can optimize the single-character deletion check, but a simple character-by-character comparison works fine. The hash table is non-negotiable.
Why is the acceptance rate 62 percent and not higher?+
The DP state transition isn't trivial, and the predecessor-lookup logic trips up candidates who haven't seen the pattern. The string manipulation (deletion testing) also introduces off-by-one bugs. It's medium difficulty genuinely. Drill the length-sorted approach and you'll be in the clear.
Want the actual problem statement? View "Longest String Chain" on LeetCode →