Array

LeetCode 2537 note: adding x creates cnt[x] new equal pairs and removing it loses cnt[x] - 1; an “at least k pairs” counting window with count += left

LeetCode 2962 note: an “at least k” counting window: keep shrinking while the max appears k times, after which every left end in [0, left) is valid, so count += left

LeetCode 2968 note: after sorting, the cheapest common target for a block is its median; prefix sums give the cost in O(1), and it grows with the window, so slide

LeetCode 2875 note: strip target // sum full cycles; the remainder is smaller than one cycle, so a sliding window over two copies of nums always finds it

LeetCode 2302 note: score = sum × length with positive numbers grows with the window; shrink while the score is >= k, and right - left + 1 valid subarrays end at right

LeetCode 1040 note: max moves = total gaps minus the edge gap the first move wastes; min moves uses a length-n window holding the most stones, with a special case of 2 when n - 1 stones are already consecutive and one is far away

LeetCode 3810 note: one operation fixes every position holding a value, so the answer is the number of distinct values at mismatched positions

LeetCode 3809 note: keep towers within the Manhattan radius and take the minimum by (-quality, x, y), which also handles ties

LeetCode 3413 note: the best k bags always have one end on a segment boundary; compute “left end at a segment start” and “right end at a segment end” (the latter by mirroring and reusing the same function)

LeetCode 2009 note: the result is n consecutive integers; after deduplicating and sorting, a sliding window finds the most distinct values within a span of n - 1, and the rest must change

LeetCode 2555 note: a sliding window gives how many prizes a segment ending at each prize collects, and a running “best single segment among the first i prizes” supplies the second segment to its left

LeetCode 2106 note: the harvest is always a contiguous block of fruits; covering [L, R] takes (R - L) + min(|start - L|, |R - start|) steps, so slide a window over the fruits array