Stepping Numbers
A medium-tier problem at 48% community acceptance, tagged with Math, Backtracking, Breadth-First Search. Reported in interviews at Epic Systems and 0 others.
Stepping Numbers is a medium-difficulty problem that appears in Epic Systems interviews. It combines math and graph traversal in a way that catches candidates off guard: the obvious recursive approach balloons into a brute-force mess if you don't nail the pattern first. You're building numbers where each adjacent digit differs by exactly 1, then filtering by a range. Acceptance sits around 48 percent, which means half the people walking in unprepared hit a wall. If this problem lands in your live OA and you freeze on the state-space trick, StealthCoder surfaces a working BFS or backtracking solution in seconds, invisible to the proctor.
Companies that ask "Stepping Numbers"
Stepping Numbers 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 a senior engineer who knows the OA is theater. This is the script.
Get StealthCoderThe trap is thinking you can just generate all valid stepping numbers recursively and filter. You can, but the search space explodes fast. The real move is to treat each valid number as a node in a graph and use BFS or backtracking to build only the numbers inside your target range. Start from single digits 1 through 9, then expand each by appending the next valid digit (current digit plus or minus 1). Prune aggressively: if a number exceeds your upper bound, kill that branch. The math part is just digit arithmetic; the algorithmic meat is recognizing this as a controlled traversal, not a permutation problem. Epic Systems leans on this because it tests whether you can model a constraint as a graph shape. When you're live and staring at the range bounds, StealthCoder eliminates the guesswork and gets you to the working code path.
Pattern tags
You know the problem.
Make sure you actually pass it.
Stepping Numbers 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 a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Stepping Numbers interview FAQ
Is Stepping Numbers actually asked at Epic Systems?+
Yes. It shows up in Epic's online assessments. The company reported it once in our data set, but that single report signals it's part of their rotation. Treat it as a genuine threat if you're interviewing there.
What's the trick to avoid timeout?+
Don't generate every number in the range and filter. Use BFS or backtracking to build only valid stepping numbers by extending digits one step at a time. Prune branches that exceed your upper bound immediately. This keeps the tree tight and avoids exponential blowup.
Do I need both BFS and backtracking, or is one enough?+
Either works. BFS treats stepping numbers as a queue of candidates, expanding each level by level. Backtracking explores depth-first and backtracks when you overshoot the range. Pick whichever feels cleaner to you. The acceptance rate suggests neither is obviously dominant.
How does this problem test 'Math' if it's mostly graph traversal?+
The math is the constraint itself: adjacent digits differ by exactly 1. That's arithmetic, not algorithm. You need to reason about which digits can follow a given digit (n-1 and n+1), which is mathematical reasoning. The traversal is where you implement it.
Should I precompute all stepping numbers up to some limit?+
Depends on your range. If the range is small, BFS on-the-fly is cleaner. If you're running many queries, precomputing once is smarter. For a single OA problem, on-the-fly BFS usually wins on clarity and memory.
Want the actual problem statement? View "Stepping Numbers" on LeetCode →