Path In Grid
Reported by candidates from Microsoft's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
You're hitting Microsoft's Path In Grid problem, reported August 2024. This is a breadth-first-search problem disguised as a grid traversal. Candidates either solve it clean or get tangled in state management. The trick is knowing when to use BFS over DFS, and how to track visited cells without blowing up your memory. StealthCoder will have the pattern locked if you blank on the implementation details during the live OA.
Pattern and pitfall
Path In Grid is a classic shortest-path or reachability problem on a 2D grid. BFS is the right choice because it explores level by level, guaranteeing the shortest path in an unweighted graph. The common mistake is forgetting to mark cells as visited before adding them to the queue, which causes infinite loops or duplicate work. You need to track your visited set carefully: either as a 2D boolean array or a set of tuples. Define your four directions (up, down, left, right) upfront, validate bounds on every step, and be paranoid about edge cases like single-cell grids or unreachable targets. If you blank during the OA, StealthCoder reads the grid constraints and generates the BFS skeleton in real time.
Memorize the pattern. If you can't, run StealthCoder. The proctor sees the IDE. They don't see what's behind it.
You can drill Path In Grid cold, or you can hedge it. StealthCoder runs invisibly during screen share and surfaces a working solution in under 2 seconds. The proctor sees the IDE. They don't see what's behind it. Made by an engineer who treats the OA as theater. If yours is tonight, you don't have time to grind. You have time to hedge.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as number of islands. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass Microsoft's OA.
Microsoft reuses patterns across OAs. Made by an engineer who treats the OA as theater. If yours is tonight, you don't have time to grind. You have time to hedge. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Path In Grid FAQ
Is this problem asking for shortest path or just reachability?+
The problem title doesn't specify, but Microsoft typically asks for shortest path or the path itself. BFS handles both. If you see the word 'shortest' or need to return the actual path, BFS gives you the parent pointers for free during traversal.
Do I need to handle obstacles or special cells?+
The problem text isn't included, but grid path problems often have walls, blocked cells, or conditional movement. Read the constraints carefully during the OA. If there are obstacles, skip them in your direction loop (check if the next cell is valid before adding to the queue).
Should I use a 2D visited array or a set of tuples?+
A 2D boolean array is faster and cleaner if the grid size is reasonable (up to 1000x1000). A set of tuples is more flexible if the grid is sparse or coordinates are large. Microsoft usually prefers the array for clarity.
What's the time and space complexity I should target?+
BFS visits every cell once, so O(m*n) time for a grid of m rows and n columns. Space is O(m*n) for the visited array and queue. If you're optimizing further, you're overthinking it. Microsoft expects clean BFS.
Is this still a common Microsoft question in 2024?+
Yes. Grid BFS problems are staple medium-level asks at Microsoft. Variations show up in interviews and OAs. Master the template (queue, visited set, four directions, bounds check) and you handle 80 percent of grid problems.