Stacks & Queues — Complete Guide with Interactive Walkthroughs
Master LIFO stacks, FIFO queues, and monotonic deques — parentheses matching, adjacent duplicates, recent calls, daily temperatures, and sliding window maximum. Animations included.
Linked Lists — Complete Guide with Interactive Walkthroughs
Master linked list mechanics, fast and slow pointers, and in-place reversal — insert/delete, cycle detection, k-th from end, and swap pairs without cheating into an array. Animations included.
Binary Search — Complete Guide with Interactive Walkthroughs
Master binary search on sorted arrays and answer spaces — classic templates, lower/upper bounds, 2D matrix tricks, and O(n log k) feasibility checks. Animations included.
Hashing — Complete Guide with Interactive Walkthroughs
Master hash maps and sets for O(1) lookups — existence checks, frequency counting, prefix + frequency patterns, and grouping. The most important data structure in interview prep. Animations included.
Prefix Sum — Complete Guide with Interactive Walkthroughs
Master prefix sums for O(1) subarray range queries — build the array, answer queries in constant time, split arrays in one pass, and optimize to O(1) space. Step-through animations included.
Two Pointers — Complete Guide with Interactive Walkthroughs
Master the two pointers technique for arrays and strings — opposite ends, merge walk, palindrome checks, two sum on sorted input, and subsequence matching. Step-through animations included.
Sliding Window Technique — Complete Reference with Animations
A friendly, step-by-step guide to sliding windows — from your first two-pointer problem to monotonic deques, production rate limiters, and the at-most-K trick. Interactive animations included.