Greedy

LeetCode 3545 note: reducing the number of kinds means deleting whole kinds, starting from the least frequent

LeetCode 3487 note: free deletion means picking distinct values; take every non-negative one, or only the maximum when all are negative

LeetCode 3075 note: choose k children from the happiest, where the i-th choice loses i, floored at 0

LeetCode 3074 note: apples can be split freely, so take boxes from the largest capacity until the total fits every apple

LeetCode 611 note: sort, fix the longest side k, and use two pointers for the shorter sides; when the sum is large enough every i in between works, adding j - i at once

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

LeetCode 402 note: a monotonically increasing stack; while deletions remain, pop any top larger than the current digit, then strip leading zeros

LeetCode 334 note: keep the smallest first and the smallest second that has something smaller before it; any number above second completes a triplet

LeetCode 324 note: sort, split into a small half and a large half, reverse each, and interleave with small values at even indices and large ones at odd indices

LeetCode 435 note: minimum removals = total minus the maximum kept; sort by right end and greedily keep the one ending earliest

LeetCode 397 note: even numbers are always halved; for odd numbers try +1 and -1 with memoized recursion, since n is too large for an n-sized array