Hash Tables Explained: How Hash Functions Power O(1) Lookups
How hash tables use hash functions for bucket assignment, how collision resolution works, and load factor's impact on performance.
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Tags: computer-science, data-structures, hashing
Hash Tables Explained: The Data Structure Powering Dictionaries Hash tables are one of the most important data structures in computer science. Python's , JavaScript's and , Java's , Go's — all are hash tables. They provide average O(1) insertion, lookup, and deletion, which is why they appear everywhere from database indexes to compiler symbol tables to caches. Understanding how they work explains both their performance and their failure modes. The Core Idea: Array + Hash Function A hash table is, at its core, an array of a fixed size (the backing array) combined with a hash function that maps keys to array indices. The hash function is the critical component. A good hash function: Is deterministic (same key always maps to same index) Distributes keys uniformly across buckets (avoiding…
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