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DSA

Day 1 of 140 · Week 1: Arrays, C# and Fundamentals · Foundations

Arrays and Hashing I

Hash maps and sets give O(1) lookups and are the first tool to reach for when a brute force is O(n^2). Most Blind75 easy questions reduce to a frequency count or a seen-set.

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Tasks

Search & resources

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  • NeetCode arrays and hashing playlist
  • hash map time complexity explained
  • Two Sum hash map solution C#