Reaching Points
A hard-tier problem at 34% community acceptance, tagged with Math. Reported in interviews at Coursera and 8 others.
Reaching Points shows up across Coursera, J.P. Morgan, Goldman Sachs, PayPal, and other tier-one companies, yet only about one in three candidates solve it on their first attempt. The problem looks deceptively simple: given two points and transformation rules, can you reach one from the other. The catch is that a naive BFS or DFS explodes in complexity. The actual solution lives in number theory and working backwards, not forwards. If this problem lands in your assessment and you haven't drilled the backwards-induction pattern, StealthCoder solves it invisibly while you stay calm.
Companies that ask "Reaching Points"
Reaching Points 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. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe trap is trying to simulate forward from the start point to the target. Instead, reverse the problem: work backwards from the target to the start. This transforms the search space from exponential growth into a linear or near-linear walk down a GCD-like path. The insight is recognizing that certain moves are invertible and that one direction is far more efficient than the other. The problem tests whether you can spot when the obvious approach fails and pivot to a mathematical perspective. This is a Math topic problem, not a graph traversal one, and that shift in thinking separates solvers from blanks. When you're live in the assessment and the forwards simulation times out, StealthCoder surfaces the backwards logic in real time, invisible to the proctor.
Pattern tags
You know the problem.
Make sure you actually pass it.
Reaching Points recycles across companies for a reason. It's hard-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. Made for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Reaching Points interview FAQ
Is Reaching Points still commonly asked at big tech and finance companies?+
Yes. It appears across nine companies in the data, including Coursera, J.P. Morgan, Goldman Sachs, and PayPal. The acceptance rate is 33.6%, which means it's hard enough to be a true filter but not so rare that you'd skip it during prep.
What's the main trick that makes this problem click?+
Work backwards, not forwards. Reversing the transformation rules and walking backwards from the target to the start dramatically shrinks the search space. Most candidates default to forwards simulation and hit a time-limit wall. The backwards insight is the entire problem.
How much does this problem depend on advanced math?+
You need to understand GCD, modular arithmetic, and why certain sequences converge or cycle. It's not calculus or linear algebra, but it does demand comfort thinking in terms of number properties rather than typical algorithmic patterns.
If I blank on the backwards trick during a live assessment, how screwed am I?+
Very. The forwards approach will time out. There's no partial credit for a slow brute force. This is exactly where a real-time solution hedge matters most: if you hit a wall on a Math-topic problem, you need the answer fast.
How does Reaching Points compare in difficulty to other Math-topic problems?+
At the HARD difficulty level with 33.6% acceptance, it's a genuine blocker. The problem tests insight and pattern recognition more than code volume. Many candidates can code the backwards walk once they see it, but the initial pivot from forwards to backwards is where most fail.
Want the actual problem statement? View "Reaching Points" on LeetCode →