String

LeetCode 2730 note: the window holds at most one adjacent equal pair; when a new pair arrives, shrink the left until the previous pair leaves

LeetCode 2516 note: taking from both ends leaves a middle block in which each letter may appear at most total − k times; find the longest such window

LeetCode 3090 note: a longest-window slide that shrinks the left whenever the newly added character appears more than twice

LeetCode 2024 note: a window is valid when the rarer of T and F appears at most k times (flip all of them); shrink the left when it is not

LeetCode 1208 note: each position costs |s[i] - t[i]|, so the problem becomes the longest subarray with sum <= maxCost

LeetCode 1461 note: put every length-k substring in a set and check that its size reaches 2^k; the last start is len(s) - k

LeetCode 3800 note: split mismatches into two kinds; pair different kinds with a swap, same kinds with cross + swap, flip any leftover, and compare each against two flips

LeetCode 3799 note: four nested levels pruned by corner letters; sorting the words first makes the output lexicographic

LeetCode 3798 note: parity depends only on the last digit, so just delete trailing 1s; keeping more digits is larger

LeetCode 2953 note: split where neighboring letters differ by more than 2; in each segment enumerate the number of distinct letters d, slide a fixed window of d × k, and track how many letters appear exactly k times

LeetCode 2269 note: convert the number to a string and check every length-k substring; 0 cannot be a divisor

LeetCode 2156 note: the first character has weight p^0, so sliding right to left needs only multiply by p, add the new character, and subtract the outgoing one times p^k; the modulus may not be prime, so no modular inverse