Blind 75 roadmap

The classic 75 interview problems.

For: Interviewing in 6 to 10 weeks

Arrays and Hashing

Trade memory for speed by remembering what you have already seen.

Walk a sequence from both ends, or at two speeds, to avoid nested loops.

Halve the search space each step, on sorted data or on an answer range.

Last in, first out. Use it to match pairs and undo work.

Keep a moving range valid while you slide it across the input.

Sort ranges by start so overlaps can be merged, counted and scheduled.

Rewire pointers in place, and use fast and slow pointers to find cycles and middles.

Think recursively: solve a node from the answers for its children.

Use the ordering invariant to search, insert and validate in O(height).

Always get the smallest or largest item next without sorting everything.

Share prefixes in a tree of characters for fast prefix and dictionary lookups.

Build candidates step by step and undo a choice when it cannot lead to an answer.

Traverse connected structures: islands, components, shortest hops in a grid.

Break a problem into overlapping subproblems and store each answer once.

Order tasks by their dependencies and detect cycles.

Take the locally best choice when it provably leads to a global best.

Choose items under a budget; the pattern behind coin change and partitions.

Fill a table indexed by two variables: grids, two strings, intervals.

Rotate, spiral and search 2-D arrays, and treat a grid as an implicit graph.

Work on the binary form with AND, OR, XOR and shifts.