Easy

LeetCode 598 note: every operation covers the top-left corner, so the most-incremented cells form the intersection of all operations: min(a) × min(b)

LeetCode 594 note: subsequences need not be contiguous, so just count; for each x add the counts of x and x + 1

LeetCode 590 note: post-order is each child then the node; iteratively, run a root-then-children-right-to-left pre-order and reverse the whole result

LeetCode 589 note: n-ary pre-order records the node then each child in order; flatten recursive results with extend, not by appending a list

LeetCode 575 note: at most n / 2 candies can be eaten and at most len(set) kinds exist; the answer is the smaller of the two

LeetCode 572 note: for every node of root, check whether its subtree equals subRoot; recurse with isSubtree, not by comparing only the children

LeetCode 566 note: return the original if the element counts differ; otherwise element k goes to (k // c, k % c)

LeetCode 563 note: return subtree sums in post-order; each node’s tilt is the difference of its subtree sums, added to the answer

LeetCode 561 note: sort and pair neighbors; each pair’s minimum is the element at an even index, so sum those

LeetCode 559 note: depth is 1 plus the deepest child, or 1 with no children

LeetCode 557 note: split on spaces, reverse each word, and join with spaces

LeetCode 551 note: fewer than two A’s and no LLL substring