dsa6 min read
Find K Closest Elements — Binary Search on Window Boundary
LeetCode 658 asked at Google, Amazon, and Microsoft. Binary search on the window left boundary returns the k closest elements in O(log(n-k)+k) time.
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dsa5 min read
Count Subarrays With Fixed Bounds — Three-Index Counting Trick
LeetCode 2444 asked at Google and Amazon. Track last-bad, last-minK, and last-maxK indices to count valid subarrays in a single O(n) pass.
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dsa5 min read
Max Consecutive Ones II — Flip One Zero, Track Its Index
LeetCode 487 asked at Microsoft, Meta, and Amazon. Track the last zero index instead of a counter to handle the streaming follow-up in O(n) time and O(1) space.
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dsa5 min read
Sort Vowels in a String — Extract, Sort, Reinsert Cleanly
LeetCode 2785 asked at Amazon and Microsoft. Extract vowels, sort by ASCII, then reinsert at original positions in O(n log n) time and O(n) space.
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dsa6 min read
Minimum Window Subsequence — Forward Then Backward Scan
LeetCode 727 asked at Google and Amazon. A forward scan finds a valid right boundary, then a backward scan tightens the left boundary in O(|s|*|t|) time.
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