Medium

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

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 1016 note: s has at most 1000 characters, so there are few substrings of any fixed length and a large n must be False; checking from n downward fails fast, or extend up to 30 bits from each start to collect every value <= n

LeetCode 3796 note: each position’s bound is the min of its own limit, the left bound + difference and the right bound + difference; one pass each way