LeetCode

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

LeetCode 2958 note: a longest-window slide that shrinks the left whenever the newly added number appears more than k times

LeetCode 220 note: with bucket size valueDiff + 1, two numbers in one bucket always qualify, so only the two neighboring buckets need checking; the window keeps the latest indexDiff numbers, so each bucket holds at most one

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 865 note: BFS to the last level and climb together, or one DFS returning (depth, node)

LeetCode 1339 note: compute the total, enumerate every subtree sum, and leave the input untouched

LeetCode 1975 note: minus signs can travel anywhere in pairs but the parity of the negative count never changes; with an odd count, leave one on the smallest absolute value

LeetCode 1161 note: pushing None into the next level creates a fake level with sum 0

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 1401 note: the rectangle’s nearest point to the center is the center clamped into the rectangle; they overlap when that point is within the radius

LeetCode 1306 note: indices are nodes and the two jumps are edges; BFS or DFS decides whether a zero is reachable