dsa5 min read
Minimum Size Subarray Sum — Shortest Window Reaching Target
LeetCode 209 — find the shortest contiguous subarray whose sum is at least target. A staple FAANG question on the shrinkable sliding window template.
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dsa5 min read
4Sum II — Split-and-Hash for Quadruple Counting
LeetCode 454 — count quadruples summing to zero across four arrays using meet-in-the-middle hashing. Asked at Google, Amazon, and Bloomberg.
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dsa5 min read
Container With Most Water — Greedy Two Pointers
LeetCode 11 — find two lines that hold the most water using a greedy two-pointer scan in O(n). Top-five most asked FAANG two-pointer problem.
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dsa6 min read
Boats to Save People — Greedy Sort and Two Pointers (LC 881)
LC 881 asks for the minimum boats to rescue everyone given a weight limit and at-most-2-per-boat rule. Sort then greedily pair the heaviest with the lightest using two pointers — O(n log n) time, O(1) space.
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dsa6 min read
3Sum — Sort and Two-Pointer Scan with Deduplication (LC 15)
LC 15 asks for all unique triplets summing to zero. Sort the array, fix each element as the anchor, and use two pointers to scan for pairs — with careful three-level deduplication. A must-know FAANG pattern.
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