Pattern catalog
Each card is a technique: cues, template, and a problem path. Status chip top-right; path inventory under the title (for example “6 guides and a template”); your completion counts sit on the right once you start.
Showing 1 to 9 of 37
Sliding Window
Longest, shortest, or valid contiguous ranges over arrays and strings.
6 guides and a template
Two Pointers
Sorted arrays, pair conditions, or coordinated movement from both ends.
6 guides and a template
Fast & Slow Pointers
Linked-list cycles, middle nodes, and fixed pointer gaps.
6 guides and a template
Binary Search
Halve a sorted or monotonic search space until you pin the answer.
6 guides and a template
Binary Search on Answer
Binary search the answer value itself; check if a candidate is feasible in linear time.
6 guides and a template
Hashing
O(1) average lookup, frequency counting, grouping, and complement checks.
6 guides and a template
Prefix Sum
Precompute running sums so any range sum is O(1); pair with maps for subarray sum counts.
6 guides and a template
Difference Array
Range updates in O(1); rebuild the array with a prefix pass.
6 guides and a template
Monotonic Stack
Next greater/smaller, histogram rectangles, and temperature waits.
6 guides and a template