All 26 patterns

signal · Sorted array, pair sum, or comparing elements from both ends.

5 practice problems · 45 minfree

signal · Contiguous subarray or substring with a size or condition constraint.

4 practice problems · 50 minfree

signal · Need fast lookup, frequencies, duplicates, or a complement? Store what you have seen.

5 practice problems · 50 minpro

signal · Cycle detection or middle-of-list problems.

4 practice problems · 40 minfree

signal · Repeated range-sum queries or subarrays summing to a target.

5 practice problems · 35 minpro

signal · Matching pairs, nesting, undo, or "most recent unresolved" state.

4 practice problems · 45 minpro

signal · Level order, fewest moves, arrival-order or breadth-first processing.

4 practice problems · 45 minpro

signal · Sorted or rotated sorted array, or an explicit O(log n) requirement.

4 practice problems · 45 minfree

signal · Level-order or path-based tree problems.

4 practice problems · 55 minfree

signal · "Minimise the maximum" or a feasibility check that is monotone.

5 practice problems · 50 minpro

signal · 2D grid of islands, regions, or directional walks.

5 practice problems · 45 minpro

signal · Right-side view, level averages, minimum depth.

5 practice problems · 40 minpro

signal · Path sums, diameters, subtree properties.

5 practice problems · 45 minpro

signal · Connected components, reachability, shortest hops.

5 practice problems · 60 minpro

signal · Prerequisites, build order, dependency cycles.

5 practice problems · 55 minpro

signal · Next greater/smaller element, spans, histograms.

5 practice problems · 55 minpro

signal · K largest, K closest, K most frequent.

5 practice problems · 45 minpro

signal · Running median, scheduling with two halves.

4 practice problems · 50 minpro

signal · Dynamic connectivity, redundant edges, account merging.

5 practice problems · 60 minpro

signal · Prefix search, word dictionaries, wildcard matching.

5 practice problems · 50 minpro

signal · Single number, subsets, counting bits.

6 practice problems · 45 minpro

signal · Reverse a list, a sublist, or k-sized groups.

5 practice problems · 40 minpro

signal · Optimal substructure, overlapping subproblems, "minimum / maximum / number of ways to".

5 practice problems · 90 minfree

signal · Meeting rooms, merge intervals, insert interval.

5 practice problems · 45 minpro

signal · Permutations, combinations, sudoku, word search.

5 practice problems · 70 minpro

signal · Jump game, gas station, interval scheduling.

5 practice problems · 50 minpro