DSA practice problems

151 data structures and algorithms problems, grouped by pattern, each with hints and solutions from brute force to optimal.

• Arrays & Hashing: Using arrays and hash tables to track, count, and look up values fast.
• Two Pointers: Walking two positions through a sequence at once, often from both ends inward.
• Sliding Window: Growing and shrinking a window over a sequence to track a running condition.
• Stack: Using last-in-first-out order to match, undo, or track nested structure.
• Binary Search: Cutting a sorted (or sorted-like) search space in half, repeatedly.
• Linked List: Rewiring pointers between nodes instead of shifting array elements.
• Trees: Traversing and reasoning about hierarchical, branching structures.
• Tries: A tree specialized for storing and searching sequences, like words.
• Heap / Priority Queue: Always having fast access to the smallest or largest remaining item.
• Backtracking: Exploring choices one at a time, undoing ones that don't pan out.
• Graphs: Modeling and traversing networks of connected nodes.
• Advanced Graphs: Shortest paths, minimum spanning trees, and topological ordering.
• 1-D Dynamic Programming: Building up an answer from smaller subproblems along one dimension.
• 2-D Dynamic Programming: The same idea as 1-D DP, tracked across two dimensions at once.
• Greedy: Making the locally best choice at each step and trusting it works out.
• Intervals: Comparing and merging ranges that may overlap.
• Math & Geometry: Problems that lean on numeric reasoning or 2D grid geometry.
• Bit Manipulation: Working with the individual binary bits inside a number.