6 articles
LC 62 Unique Paths is the foundational 2D grid DP problem at Amazon, Google, and Meta. Learn the recurrence, space-optimize to 1D, and master the combinatorics shortcut interviewers love to ask about.
LC 63 Unique Paths II extends the classic grid DP with obstacle cells. Master the obstacle-zeroing pattern, handle blocked start/end edge cases, and space-optimize to O(n) — the exact follow-up interviewers throw immediately after Unique Paths.
LC 64 Minimum Path Sum is the essential cost-minimization variant of grid DP, asked heavily at Amazon and Google. Learn the 2D recurrence, space-optimize to O(n), and understand why bottom-up tabulation handles borders without special-casing.
LC 120 Triangle asks for the minimum-sum path from apex to base. The bottom-up DP approach eliminates border initialization complexity and achieves O(n) space — a classic 2D DP problem that tests your ability to work on non-rectangular structures.
LeetCode 174 Dungeon Game is the textbook example of why DP direction matters. We derive why forward DP fails, build the backward dp[i][j] = max(1, ...) recurrence, dry-run the grid, and finish with a space-optimized 1D solution loved at FAANG.
LeetCode 931 Minimum Falling Path Sum is the cleanest grid DP with diagonal moves. We derive the dp[i][j] recurrence with three predecessors, walk a full table, and ship an O(1) extra-space in-place tabulation that interviewers love.