National Instruments coding interview
questions, leaked.
4 problems reported across recent National Instruments interviews. Top patterns: dynamic programming, array, stack. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
National Instruments pulls 4 problems from a narrow but demanding set. Three are medium, one hard. You're looking at dynamic programming twice, array and stack twice each. This isn't a wide net. The company is testing whether you can recognize patterns fast and code them under pressure. Trapping Rain Water is the killer here, hitting five different techniques in one problem. If you blank on the monotonic-stack approach mid-OA, StealthCoder surfaces the solution invisible to the proctor. The other three are standard medium-tier: string manipulation with a stack, DP simulation, BFS on a grid. Prep tight, not wide.
Top problems at National Instruments
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Decoded String at Index | MEDIUM | 100.0 | 37% | String · Stack |
| 02 | Champagne Tower | MEDIUM | 85.3 | 58% | Dynamic Programming |
| 03 | Trapping Rain Water | HARD | 74.6 | 65% | Array · Two Pointers · Dynamic Programming |
| 04 | Snakes and Ladders | MEDIUM | 66.0 | 48% | Array · Breadth-First Search · Matrix |
Frequencies derived from public community-tagged interview reports. Click a row to view on LeetCode.
You have a week, maybe less. You can't out-grind the list above. StealthCoder runs invisibly during the actual National Instruments OA. The proctor cannot see it. Screen share cannot detect it. Built by a senior engineer who knows the OA is theater. This is the script.
Get StealthCoder- dynamic programming2 · 50%
- array2 · 50%
- stack2 · 50%
- two pointers1 · 25%
- monotonic stack1 · 25%
- breadth first search1 · 25%
- matrix1 · 25%
- string1 · 25%
Dynamic programming dominates the signal. Champagne Tower is a classic simulation problem that rewards careful state tracking. Trapping Rain Water is the pressure test, and most candidates freeze on it because they try brute force first. Array and stack problems cluster around the same intuition: scan, maintain order, pop when needed. Two pointers appears once but sits inside Trapping Rain Water, so drilling that problem teaches you the pattern. Breadth-first search on the matrix (Snakes and Ladders) is the outlier, but it's a straightforward BFS if you set up the graph right. Start with Champagne Tower to warm up DP logic, then hit Trapping Rain Water hard because it's where most candidates lose time. Stack and two-pointer patterns reinforce each other, so drill them back-to-back. StealthCoder is your hedge if the monotonic-stack logic doesn't click during the live assessment.
Companies with similar patterns
If you prepped for National Instruments, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass National Instruments.
Memorizing every problem above in a week is a fantasy. StealthCoder is the hedge: an AI overlay that's invisible during screen share. It reads the problem on screen and surfaces a working solution in under 2 seconds. Built by a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
National Instruments interview FAQ
Should I study dynamic programming first for National Instruments?+
Yes. DP appears twice in their problem set, and Champagne Tower is the easier entry point. Trapping Rain Water also uses DP as one solution path. Drilling DP first gives you confidence and a pattern you can adapt quickly if a new variant appears in the OA.
How much time should I spend on stack problems for this company?+
Stack comes up twice and overlaps heavily with other patterns. Decoded String at Index uses stack for parsing. Trapping Rain Water uses monotonic stack. Spend time on both, but frame them as pattern recognition, not rote memorization. One solid drill of each should be enough.
Is Trapping Rain Water actually as hard as the difficulty says?+
It's listed hard and it is. It combines five topics. Brute force is slow. Two-pointer works if you think through it. Monotonic stack is optimal. Most candidates run out of time or get stuck on the first approach. This is the problem that separates prepared from unprepared at National Instruments.
Do I need to know BFS well for this company?+
It appears once in Snakes and Ladders. If you're solid on BFS basics and can model a board as a graph, you're fine. It's not their primary signal. DP and arrays matter more. But don't skip it, because BFS on a matrix is a common follow-up question.
What's the best order to drill these four problems?+
Start with Champagne Tower to build DP intuition. Then Decoded String at Index for stack basics. Then Snakes and Ladders for BFS practice. Hit Trapping Rain Water last, when you're warmed up. It's the hardest and rewards solid fundamentals in other patterns.