{"id":14485,"date":"2024-03-15T09:14:59","date_gmt":"2024-03-15T09:14:59","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-is-the-unordered_set-used-in-c\/"},"modified":"2025-08-06T09:19:26","modified_gmt":"2025-08-06T09:19:26","slug":"how-is-the-unordered_set-used-in-c","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-is-the-unordered_set-used-in-c\/","title":{"rendered":"Using unordered_set in C++"},"content":{"rendered":"

The unordered_set is a type of unordered collection container in the C++ standard library that stores unique elements. It is implemented based on a hash table data structure, providing fast element lookup, insertion, and deletion operations.<\/p>\n

Here is how to use the unordered_set:<\/p>\n

    \n
  1. Include the header file: header file needs to be included.<\/li>\n
  2. Definition of a container: Using the std::unordered_set template to define an unordered_set object, one can specify the element type and hash function.<\/li>\n<\/ol>\n
    #include<\/span> <unordered_set><\/span><\/span>\r\n\r\nstd::unordered_set<int<\/span>> mySet; \/\/ \u5b9a\u4e49\u4e00\u4e2a\u5b58\u50a8int\u7c7b\u578b\u5143\u7d20\u7684unordered_set<\/span>\r\n<\/code><\/pre>\n
      \n
    1. add<\/li>\n<\/ol>\n
      mySet.insert<\/span>(10<\/span>); \/\/ \u63d2\u5165\u5143\u7d2010<\/span>\r\nmySet.insert<\/span>(20<\/span>); \/\/ \u63d2\u5165\u5143\u7d2020<\/span>\r\n<\/code><\/pre>\n
        \n
      1. delete<\/li>\n<\/ol>\n
        mySet.erase<\/span>(10<\/span>); \/\/ \u5220\u9664\u5143\u7d2010<\/span>\r\n<\/code><\/pre>\n
          \n
        1. locate<\/li>\n<\/ol>\n
          std::unordered_set<int<\/span>>::iterator it = mySet.find<\/span>(20<\/span>);\r\nif<\/span> (it != mySet.end<\/span>()) {\r\n    \/\/ \u5143\u7d20\u5b58\u5728<\/span>\r\n} else<\/span> {\r\n    \/\/ \u5143\u7d20\u4e0d\u5b58\u5728<\/span>\r\n}\r\n<\/code><\/pre>\n
            \n
          1. Iterate elements: Traverse all elements in an unordered_set using iterators.<\/li>\n<\/ol>\n
            for<\/span> (std::unordered_set<int<\/span>>::iterator it = mySet.begin<\/span>(); it != mySet.end<\/span>(); ++it) {\r\n    \/\/ \u5904\u7406*it<\/span>\r\n}\r\n<\/code><\/pre>\n
            The unordered_set also provides some other commonly used member functions, such as empty to check if the unordered_set is empty, size to return the number of elements in the unordered_set, and clear to remove all elements from the unordered_set.<\/p>\n
            It is important to note that elements in an unordered_set are not ordered. The average time complexity for insertion and searching operations is constant O(1), but in the worst case scenario it may reach linear O(n).<\/p>\n","protected":false},"excerpt":{"rendered":"
            The unordered_set is a type of unordered collection container in the C++ standard library that stores unique elements. It is implemented based on a hash table data structure, providing fast element lookup, insertion, and deletion operations. Here is how to use the unordered_set: Include the header file: header file needs to be included. Definition of […]<\/p>\n","protected":false},"author":9,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[5148,19555,381,647,19554],"class_list":["post-14485","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-c-containers","tag-c-hash-table","tag-c-programming","tag-c-standard-library","tag-unordered_set-c"],"yoast_head":"\nUsing unordered_set in C++ - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn how to use unordered_set in C++. 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