- 3. Longest Substring Without Repeating Characters โ HashSet works, but HashMap lets you jump
leftdirectly instead of moving one step at a time - 424. Longest Repeating Character Replacement โ
maxfnever decreases; window only grows when we find something better - 340. Longest Substring with At Most K Distinct Characters โ generalized version of 159
- 159. Longest Substring with At Most Two Distinct Characters โ same as 340, just K = 2
- 992. Subarrays with K Different Integers โ
exactly K = atMost(K) - atMost(K-1), also solvable with 3-pointer trick