Curate the practice that builds intuition.

Given an array and window size k, return the maximum sum of any contiguous window — without recomputing.

Return the length of the longest substring with all distinct characters.

Given coin denominations and an amount, return the minimum number of coins, or -1 if impossible.

Reverse a singly linked list in place and return the new head.

Given begin/end words and a dictionary, return the shortest transformation sequence length.