Longest Increasing Path in a Matrix
Mountain Trail Finder You're building a hiking app that finds the longest uphill trail in a terrain map. Given a grid where each cell represents elevation, find the longest path where each step moves to a strictly higher elevation. You can move up, down, left, or right. Example: [[9,9,4],[6,6,8],[2,1,1]] → 4 (path: 1→2→6→9)
This one is about turning repeated work into a reusable state instead of re-solving subproblems. It's a hard one for a reason: it stresses state-and-transition thinking when the rules pile up. Don't rush the code—spend your time nailing the state definition first.
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