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LeetCode 88 Merge Sorted Array is the classic three pointer in-place merge problem at Microsoft, Bloomberg, and Amazon. Walk both arrays from the end into the trailing empty slots to achieve O(m plus n) time with O(1) extra space.
LeetCode 392 Is Subsequence is a Google and Amazon greedy two pointer problem. Walk both strings forward, advance the source pointer only on matches, and answer in O(m plus n) time with O(1) space.
LeetCode 1004 Max Consecutive Ones III is a Google and Amazon variable sliding window problem. Track the count of zeros inside the window and shrink from the left whenever it exceeds k to find the longest contiguous run of ones after k flips.
LeetCode 1176 Diet Plan Performance is a Google fixed sliding window problem. Maintain a running sum of exactly k consecutive calories to score points or penalties in O(n) time and O(1) space.
LeetCode 1480 Running Sum of 1D Array introduces the prefix sum technique used in dozens of FAANG range query problems. Build the running sum in O(n) time and O(1) extra space and unlock LC 303, LC 560, and LC 974.