Explore: coding interview guides
15 guides, each teaching one coding interview pattern and ending with the problems to practise it. Free to read.
- Arrays & Strings 101 Master the in-place tricks and index arithmetic behind most first-round questions.
- Hash Map & Set 101 Turn slow nested loops into one pass by remembering what you have already seen.
- Two Pointers 101 Walk an array from both ends and replace an O(n²) search with a single pass.
- Sliding Window 101 Answer every 'best contiguous subarray' question by growing and shrinking one window.
- Prefix Sum 101 Precompute running totals once and answer any range-sum question instantly.
- Stack & Queue 101 Use last-in-first-out to match brackets, undo steps and find the next greater value.
- Linked List 101 Rewire nodes confidently with dummy heads, fast-slow pointers and in-place reversal.
- Sorting & Binary Search 101 Halve the search space every step, on arrays and on the answer itself.
- Binary Trees 101 Think recursively: solve the tree by trusting the answer from each subtree.
- Heaps & Priority Queues 101 Keep the best k items at hand and always process the most urgent one next.
- Graphs 101 Model the problem as nodes and edges, then let BFS, DFS or Dijkstra do the work.
- Greedy & Intervals 101 Make the locally best choice, and learn how to prove it is also globally best.
- Math & Bits 101 Use XOR, powers of two and number tricks to solve problems in a few lines.
- Backtracking 101 Explore every choice with one clean recursive template, and prune what cannot work.
- Dynamic Programming 101 Define the state, write the recurrence, and let a table remember every subproblem.