--- title: What is a Hash Map? Time Complexity and Two Sum Example description: Learn about constant and linear time complexity, the use of hash maps, and how to solve the Two Sum problem using a hash table. canonical: https://daily.dev/posts/what-is-a-hash-map-time-complexity-and-two-sum-example-fdlzfurww twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: What is a Hash Map? Time Complexity and Two Sum Example | daily.dev og:description: Learn about constant and linear time complexity, the use of hash maps, and how to solve the Two Sum problem using a hash table. og:url: https://daily.dev/posts/what-is-a-hash-map-time-complexity-and-two-sum-example-fdlzfurww og:image: https://api.daily.dev/og/posts/FdLzfuRwW.png og:image:alt: What is a Hash Map? Time Complexity and Two Sum Example og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # What is a Hash Map? Time Complexity and Two Sum Example **[freeCodeCamp](https://daily.dev/sources/freecodecamp)** · 7 min read · 19 upvotes · 0 comments ## Summary Learn about constant and linear time complexity, the use of hash maps, and how to solve the Two Sum problem using a hash table. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: --- Tags: [#data-science](https://daily.dev/tags/data-science), [#general-programming](https://daily.dev/tags/general-programming), [#time-complexity](https://daily.dev/tags/time-complexity) [View this post on daily.dev](https://daily.dev/posts/what-is-a-hash-map-time-complexity-and-two-sum-example-fdlzfurww) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"What is a Hash Map? Time Complexity and Two Sum Example","url":"https://daily.dev/posts/what-is-a-hash-map-time-complexity-and-two-sum-example-fdlzfurww","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/what-is-a-hash-map-time-complexity-and-two-sum-example-fdlzfurww"},"datePublished":"2024-01-25T19:19:37.631Z","dateModified":"2026-03-15T04:52:38.876Z","description":"Learn about constant and linear time complexity, the use of hash maps, and how to solve the Two Sum problem using a hash table.","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/44a7087523bcca12035f02dfcf1be795?_a=AQAEufR","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/44a7087523bcca12035f02dfcf1be795?_a=AQAEufR","isAccessibleForFree":true,"articleSection":"freeCodeCamp","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"freeCodeCamp","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1628412854/logos/freecodecamp","url":"https://daily.dev/sources/freecodecamp"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/what-is-a-hash-map-time-complexity-and-two-sum-example-fdlzfurww","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":19},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"data-science,general-programming,time-complexity","timeRequired":"PT7M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"freeCodeCamp","item":"https://daily.dev/sources/freecodecamp"},{"@type":"ListItem","position":3,"name":"What is a Hash Map? Time Complexity and Two Sum Example"}]} ```