Ant on the Boundary
A easy-tier problem at 74% community acceptance, tagged with Array, Simulation, Prefix Sum. Reported in interviews at Accenture and 0 others.
Ant on the Boundary is a straightforward array simulation problem that appears deceptively simple on first read. The catch is that many candidates overthink it or miss the pattern entirely when they see it live. With a 74% acceptance rate, it's one of those problems where the trick matters more than raw complexity. Accenture has asked it. If you hit this during an assessment and blank on the state-tracking logic, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Ant on the Boundary"
Ant on the Boundary 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 core insight is that you're simulating an ant's position as it reads through an array of instructions, tracking whether it ever crosses a boundary. Most candidates try to build complex state machines or overthink edge cases. The real pattern is simpler: maintain a running position, check the boundary condition at each step, and return early if crossed. The pitfall is forgetting that the ant starts at position zero and that positive or negative directions depend on instruction values. When you get stuck on the live assessment trying to balance off-by-one errors or array indexing, StealthCoder runs invisibly during screen share and gives you the clean simulation loop you need.
Pattern tags
You know the problem.
Make sure you actually pass it.
Ant on the Boundary 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.
Ant on the Boundary interview FAQ
Is Ant on the Boundary actually easy, or does the title lie?+
It's genuinely easy once you see the pattern. The 74% acceptance rate reflects that most people get it right, but live interview pressure and overthinking cause failures. It's a state-tracking exercise, not a heavy algorithm problem.
What's the most common mistake candidates make?+
Off-by-one errors on the boundary check and forgetting initial position. Some also confuse the direction logic or try to precompute values instead of simulating step by step. Simulation beats optimization here.
Do I need prefix sums for this problem?+
No. Prefix sum is listed as a topic but the optimal solution is pure simulation. You iterate once, track position, and return when the boundary condition hits. Prefix sum knowledge helps you think about the problem structure, not solve it.
How does this relate to array problems in real interviews?+
It's a warm-up. Most array interview problems require you to manipulate or traverse a collection intelligently. This one teaches clean state tracking and early termination, which scale to harder problems like two-pointer or sliding window.
Is Accenture the only company asking this?+
It's reported once in the data, but that doesn't mean it's unique to Accenture. Lower-frequency problems often appear across multiple companies. If it's on your prep list, it's worth drilling the simulation pattern.
Want the actual problem statement? View "Ant on the Boundary" on LeetCode →