String

LeetCode 3952 note: each token moves left at most once, so the state is whether this index’s token moved left; moving only helps if the index to the left was not already covered

LeetCode 3931 note: check that every pair of adjacent digits differs by at most 2

LeetCode note for Decode Ways, rebuilt from the original learning note

LeetCode note for Word Break, rebuilt from the original learning note

LeetCode 3913 note: extract only the vowels, sort by (-count, first occurrence), and put them back into the vowel positions

LeetCode 3900 note: equal prefix differences mean balanced; a substring off by 2 also works if a swappable character exists outside, and keeping the two earliest positions per difference is enough

LeetCode 522 note: the longest uncommon subsequence is always a whole string; check strings from longest to shortest, and the first that is not a subsequence of any other long-enough string is the answer

LeetCode 3884 note: compare from both ends toward the middle; the first match is the answer, and odd lengths always match in the middle

LeetCode 1023 note: two pointers character by character; anything beyond the pattern must be lowercase

LeetCode 3839 note: words sharing the first k characters are connected, so count by word[:k]; exclude words shorter than k

LeetCode 3838 note: sum each word’s letter weights mod 26 and map backward: 0 -> z, i.e. chr(ord(‘z’) - r)

LeetCode 244 note: precompute each word’s positions (sorted by construction), then answer each query by merging the two position lists with two pointers, always advancing the smaller one