https://algorithmsin60days.com/tags/hash-tables/Recent content in Hash-Tables on Algorithms in 60 DaysHugoen-usFri, 10 Jul 2026 00:00:00 +0000https://algorithmsin60days.com/topics/hashing/Fri, 10 Jul 2026 00:00:00 +0000https://algorithmsin60days.com/topics/hashing/<p>Hashing turns a key into an array index by running it through a hash function, so a <strong>hash table</strong> can store and retrieve values in expected constant time. Python&rsquo;s <code>dict</code> and <code>set</code> are hash tables. That average O(1) lookup is the single most useful tool in interview problem solving: an enormous fraction of &ldquo;make it faster than brute force&rdquo; questions come down to &ldquo;put it in a hash map.&rdquo;</p> <h2 id="why-hashing-matters">Why Hashing Matters<a class="header-anchor" href="#why-hashing-matters" aria-label="Permalink to this heading">#</a></h2> <p>The pattern is almost mechanical. A nested loop that checks every pair is O(n^2); a hash map that remembers what you have already seen makes it O(n). Two Sum, group anagrams, subarray sum equals k, first unique character, and detecting duplicates are all this trade: spend O(n) memory to buy O(n) time. Recognizing when to swap a scan for a lookup is a core interview skill.</p>