Use maps, sets, counters, and prefix state to make repeated lookups cheap.

0/11 solved | 11 due

Move two indexes through a sorted or constrained sequence to avoid nested loops.

0/3 solved | 3 due

Maintain a valid contiguous window while expanding and shrinking it.

0/4 solved | 4 due

Use last-in-first-out state for matching, monotonic order, or deferred work.

0/1 solved | 1 due

Cut the search space in half when the answer is ordered or monotonic.

0/2 solved | 2 due

Manipulate pointers carefully with dummy nodes, fast/slow runners, and reversal.

0/5 solved | 5 due

Use recursion or a stack to compute information from subtrees.

0/10 solved | 10 due

Use a queue to process trees level by level.

0/1 solved | 1 due

Keep only the most important candidates with a priority queue.

0/3 solved | 3 due

Explore choices recursively, undoing each choice before trying the next.

0/4 solved | 4 due

Traverse nodes with visited state to explore components, paths, and dependencies.

0/7 solved | 7 due

Sort ranges and reason about overlap, gaps, and merged boundaries.

0/5 solved | 5 due

Store best answers for prefixes, positions, or remaining amounts.

0/11 solved | 11 due

Use a matrix or two-dimensional state when decisions depend on two indexes.

0/3 solved | 3 due

Use binary operations for flags, parity, masks, and arithmetic shortcuts.

0/5 solved | 5 due