LeetCode

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

LeetCode 543 note: the diameter may skip the root; return heights in post-order while updating the answer with left + right height at every node, counting edges

LeetCode 541 note: in every block of 2k reverse the first k; when fewer than k remain reverse them all, which slicing handles automatically