字符串

Generate all string permutations using recursive backtracking, deduplicate them, and sort them lexicographically.

Use a map to count character occurrences while preserving input order to find the first character that appears only once in a stream.

Record two implementations of cyclic left rotation of a string: slicing and concatenation, and three reversals.

Sort five cards, treat jokers as 0, and use the gaps between non-zero cards to determine whether they can form a straight.

Record two implementations for replacing spaces with %20: character-by-character concatenation and preallocated storage.

Record character parsing and atoi implementations for converting a string to an integer.

Record methods for reversing word order by splitting the string and by reversing twice.