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Hash Tables

Key-value lookup in near-constant time.

4 subjects · 4 topics · 3 cheatsheets

Subjects covering this category

4 subjects
  • Subject · Beginner to Advanced

    Java

    Writing Java that compiles, runs, and models a problem with objects.

    • The Language
    • Objects
    • When Things Go Wrong
    15 topics · 131 cardsnot started
  • Subject · Intermediate to Advanced

    Java Collections and Streams

    Holding data in the right Java collection, and transforming it without writing a loop.

    • Collections
    • Pipelines
    9 topics · 78 cardsnot started
  • Subject · Beginner to Advanced

    Data Structures

    Choosing a data structure by the cost of its operations, and implementing arrays, linked lists, stacks, queues, hash tables, trees, heaps, tries and graphs in Python, Java and TypeScript.

    • Measuring Cost
    • Sequences and Lookup
    • Recursion and Trees
    15 topics · 122 cardsnot started
  • Subject · Intermediate to Advanced

    Coding Interview Patterns

    Recognising which of the common problem-solving patterns an unseen coding problem needs, and solving it in Python, Java or TypeScript within the time an interview allows.

    • Approach
    • Array and Number Patterns
    • Linked List Patterns
    17 topics · 135 cardsnot started

Cheatsheets

3 cheatsheets
  • Cheatsheet · Java Collections and Streams

    Java Collections

    Every everyday Java collection on one page: what each one is for, what it costs, and how to choose.

    3 entries here
  • Cheatsheet · Data Structures

    Data Structures

    Every data structure in the subject on one page: what each one is for, what its operations cost, and how to choose.

    1 entry here
  • Cheatsheet · Coding Interview Patterns

    Coding Interview Patterns

    Fourteen coding interview patterns on one page: the property that points to each, what it costs, when it fails, and its loop in Python.

    1 entry here

In Hash Tables itself

4 topics
  • Data Structures

    Hash Tables

    Hash tables: the data structure that turns a key into an array index to find values in expected constant time, and what collisions, growth and bad keys do to it.

    Beginner to Intermediate10 cards · 6 qnot started

  • Java Collections and Streams

    Maps and HashMap Internals

    How a HashMap works: hashing to a bucket, collisions, resizing, the three map classes, and null keys.

    Intermediate to Advanced9 cards · 5 qnot started

  • Coding Interview Patterns

    Hash Map Patterns

    Hash map patterns: complements, counts and canonical keys that turn a search inside a loop into one lookup, and the array used as its own hash map.

    Intermediate to Advanced8 cards · 4 qnot started

  • Java

    equals, hashCode and toString

    Java equals, hashCode and toString: the defaults every object inherits, the contract between equals and hashCode, and how hash maps lose keys.

    Intermediate to Advanced8 cards · 6 qnot started