Stack

LeetCode 488 note: with at most 16 balls on the board and 5 in hand, memoize DFS on the whole (board, hand) state, inserting only before a same-colored ball or between two equal balls

LeetCode 3834 note: a stack simulation where a new element merges with an equal top, possibly again with the new top

LeetCode 3816 note: a monotonic stack that deletes a larger top while another copy exists, then trims duplicate letters off the end since a prefix is always smaller

LeetCode 394 note: on [ push the current string and count, on ] pop and combine; counts can have several digits

LeetCode 3703 note: repeated replace is O(n^2); a stack of (character, run length) removes k ( plus k ) as soon as they line up

Solving the Online Stock Span problem using monotonic stack approach

Solving the Car Fleet problem using stack-based approach

Solving the Largest Rectangle in Histogram problem using monotonic stack approach

Solving the Daily Temperatures problem using monotonic stack approach

Solving the Valid Parentheses problem using stack-based approach

Implementing a stack with O(1) minimum retrieval using tuple-based approach

Solving the Reverse Polish Notation evaluation problem using stack-based approach