String

LeetCode 748 note: count the plate’s letters in lowercase, then find the shortest word covering every count, taking the earliest on ties

LeetCode 709 note: an uppercase letter plus 32 in ASCII is its lowercase form; other characters stay

LeetCode 696 note: split the string into runs of equal characters; each adjacent pair of runs contributes min(previous, current) substrings

LeetCode 680 note: at the first mismatch the only options are deleting the left or the right character; check whether either remainder is a palindrome

LeetCode 657 note: returning to the origin means as many U as D and as many L as R

LeetCode 606 note: output in pre-order, keeping an empty () when only the left subtree is missing, and omitting the right parentheses when it is empty

LeetCode 599 note: map list1’s strings to indices, sum both indices while scanning list2, and keep every string with the minimum sum

LeetCode 557 note: split on spaces, reverse each word, and join with spaces

LeetCode 551 note: fewer than two A’s and no LLL substring

LeetCode 541 note: in every block of 2k reverse the first k; when fewer than k remain reverse them all, which slicing handles automatically

LeetCode 521 note: identical strings give -1; otherwise the longer string itself is the answer

LeetCode 520 note: only three forms are valid: all caps, all lowercase, or only the first letter capitalized