1582 articles
LC 1052 maximizes satisfied customers by finding the optimal k-minute grumpiness suppression window. Decompose into a fixed base plus a variable bonus — then find the max-bonus window with a standard fixed-size sliding window. O(n) time, O(1) space.
LC 1984 asks for the minimum max-minus-min over any k chosen scores. The optimal k scores are always contiguous in sorted order — sort once then scan windows of size k in O(n log n) time, O(1) space.
LC 1208 asks for the longest substring of s transformable to t within total cost maxCost, where each character costs the absolute ASCII difference. Classic variable sliding window: expand right, shrink left while cost exceeds budget. O(n) time, O(1) space.
LC 1358 counts substrings containing at least one a, b, and c. Track the last-seen index of each character — the count of valid substrings ending at position i is min(last_seen) + 1. O(n) time, O(1) space.
LC 974 counts subarrays whose sum is divisible by k using prefix sums modulo k and a frequency map of remainders. O(n) time, O(k) space. The standard FAANG pattern for all modular subarray problems.