N-th Tribonacci Number
A easy-tier problem at 64% community acceptance, tagged with Math, Dynamic Programming, Memoization. Reported in interviews at Coursera and 2 others.
The N-th Tribonacci Number looks like a warmup. Easy difficulty, 63.6% acceptance, and it's showing up at Coursera, TCS, and Accenture. Don't let that fool you. This is the kind of problem that separates candidates who can code from candidates who understand why their code works. You'll see it in assessments and phone screens, and if you haven't prepped the pattern, you'll waste 5 minutes on the naive recursive approach before realizing it's slow. That's where StealthCoder becomes your edge: if this hits your live OA and you blank on the trick, it surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "N-th Tribonacci Number"
N-th Tribonacci Number 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 StealthCoderTribonacci is just Fibonacci's slightly weird cousin: T(n) = T(n-1) + T(n-2) + T(n-3). The trap is recursion without memoization. Naive recursion recomputes the same subproblems hundreds of times. You need Dynamic Programming or Memoization to cache results and run in linear time. The input data shows acceptance is solid but not outstanding. That gap comes from candidates submitting the inefficient version and hitting time limits, or forgetting base cases. The topics confirm this: Math, Dynamic Programming, and Memoization all apply. Most solutions use a simple array or hash map to store computed values, then iterate or recurse with lookups. If you're stuck on the live assessment, StealthCoder runs the optimal solution invisibly during your screen share, letting you understand the pattern and move on.
Pattern tags
You know the problem.
Make sure you actually pass it.
N-th Tribonacci Number 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 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.
N-th Tribonacci Number interview FAQ
What's the trick to Tribonacci that I'm missing?+
Memoization or bottom-up DP. The naive recursive approach recalculates the same values exponentially. Store computed results in a dictionary or array. Then each subproblem is solved once. Time drops from exponential to linear. That's the difference between a timeout and acceptance.
Is this really asked at FAANG or just mid-market?+
The input shows Coursera, TCS, and Accenture. It's not a FAANG-exclusive, but it's definitely part of standard screening. Easy difficulty means it's used as a baseline: can you write clean DP code under pressure. Miss this and harder problems sink you.
How does Tribonacci differ from Fibonacci in terms of prep?+
Pattern is identical: base cases, then recurrence. Tribonacci has one more term in the sum, so you track three values instead of two. If you've drilled Fibonacci with memoization, Tribonacci takes 2 minutes. Without that foundation, you're reinventing the wheel during your OA.
What's the space and time complexity I should memorize?+
Memoization or DP array: O(n) time, O(n) space. Space-optimized version: O(n) time, O(1) space (just track the last three values). The second one impresses. Most candidates submit the first and move on.
Why is acceptance only 63.6% for an easy problem?+
Candidates either submit slow recursive code, forget base cases, or don't understand why their solution is inefficient. Easy doesn't mean trivial. The input data confirms Math and DP are both required knowledge. One or the other missing costs you the solve.
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