Two Pointers
Opposite direction, same direction, and fast-slow pointer patterns
Sliding Window
Fixed and variable size windows for substring and subarray problems
Binary Search
Classic binary search, search space reduction, and rotated array variations
Prefix Sum
Range sum queries, 2D prefix sum, and difference arrays
Monotonic Stack
Next greater element, largest rectangle in histogram, and daily temperatures
Top K Elements
Heap-based solutions for Kth largest, top K frequent, and merge K sorted
Intervals
Merge intervals, insert interval, meeting rooms, and non-overlapping intervals