LeetCode

LeetCode 1480 note: the definition of a prefix sum, adding each element to the previous running total

LeetCode 1413 note: the start value plus every prefix sum must be at least 1, so it is max(1, 1 - minimum prefix sum)

LeetCode 2335 note: the answer is max(the largest count, ceil(total / 2)); simulating means filling one cup from each of the two largest every second

LeetCode 2231 note: odd digits swap only with odd digits and even with even; sort each group and refill each position with the largest digit of its parity

LeetCode 2099 note: pick the k largest values along with their indices, then sort by index to restore the original order

LeetCode 1791 note: the center lies on every edge, so the common endpoint of the first two edges is the answer

LeetCode 2357 note: each operation zeroes the group of the smallest positive value, so the answer is the number of distinct positive values

LeetCode 1464 note: all values are positive, so take the two largest a and b and return (a - 1)(b - 1)

LeetCode 1337 note: soldiers come first in each row, so binary search the first 0 for the count; sort by (count, row index) and take k

LeetCode 165 note: split on dots, compare revision by revision as integers, and treat missing revisions of the shorter version as 0

LeetCode 109 note: take the middle found with fast and slow pointers as the root and recurse on both halves; the height balances naturally

LeetCode 236 note: recursion returns whichever of p or q a subtree contains; finding something on both sides means they split here, so this node is the LCA