{"id":14204,"date":"2024-03-15T08:40:17","date_gmt":"2024-03-15T08:40:17","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-to-use-a-mapping-table-in-c\/"},"modified":"2025-08-06T05:22:23","modified_gmt":"2025-08-06T05:22:23","slug":"how-to-use-a-mapping-table-in-c","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-to-use-a-mapping-table-in-c\/","title":{"rendered":"C++ Map Guide: std::map &#038; unordered_map"},"content":{"rendered":"<p>Maps in C++ can be implemented using std::map or std::unordered_map, which are located in the <unordered_map> standard library.<\/p>\n<p>When using std::map, include the header file and declare and initialize a map using the following syntax:<\/p>\n<pre class=\"post-pre\"><code>std::map&lt;KeyType, ValueType&gt; myMap;\r\n<\/code><\/pre>\n<p>KeyType indicates the type of the key, while ValueType indicates the type of the value.<\/p>\n<p>When using std::unordered_map, you need to include the <unordered_map> header file, and declare and initialize a map using the following syntax:<\/p>\n<pre class=\"post-pre\"><code>std::unordered_map&lt;KeyType, ValueType&gt; myMap;\r\n<\/code><\/pre>\n<p>Similarly, KeyType represents the type of key, while ValueType represents the type of value.<\/p>\n<p>Common operations of a mapping table include inserting, searching, and deleting elements, with specific methods as follows:<\/p>\n<ol>\n<li>Insert element:<\/li>\n<\/ol>\n<pre class=\"post-pre\"><code>myMap.<span class=\"hljs-built_in\">insert<\/span>(std::<span class=\"hljs-built_in\">make_pair<\/span>(key, value));\r\n<span class=\"hljs-comment\">\/\/ \u6216\u8005<\/span>\r\nmyMap[key] = value;\r\n<\/code><\/pre>\n<ol>\n<li>Search for elements.<\/li>\n<\/ol>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">if<\/span> (myMap.<span class=\"hljs-built_in\">find<\/span>(key) != myMap.<span class=\"hljs-built_in\">end<\/span>()) {\r\n    <span class=\"hljs-comment\">\/\/ \u5143\u7d20\u5b58\u5728<\/span>\r\n    ValueType value = myMap[key];\r\n} <span class=\"hljs-keyword\">else<\/span> {\r\n    <span class=\"hljs-comment\">\/\/ \u5143\u7d20\u4e0d\u5b58\u5728<\/span>\r\n}\r\n<\/code><\/pre>\n<ol>\n<li>Remove elements.<\/li>\n<\/ol>\n<pre class=\"post-pre\"><code>myMap.<span class=\"hljs-built_in\">erase<\/span>(key);\r\n<\/code><\/pre>\n<p>Additionally, you can also use an iterator to traverse all elements of the map.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">for<\/span> (<span class=\"hljs-keyword\">auto<\/span> it = myMap.<span class=\"hljs-built_in\">begin<\/span>(); it != myMap.<span class=\"hljs-built_in\">end<\/span>(); ++it) {\r\n    KeyType key = it-&gt;first;\r\n    ValueType value = it-&gt;second;\r\n    <span class=\"hljs-comment\">\/\/ \u5904\u7406\u5143\u7d20<\/span>\r\n}\r\n<\/code><\/pre>\n<p>These are the basic uses of mapping tables, and depending on specific needs, other functions such as modifying element values and obtaining the size of the mapping table can also be utilized.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Maps in C++ can be implemented using std::map or std::unordered_map, which are located in the standard library. When using std::map, include the header file and declare and initialize a map using the following syntax: std::map&lt;KeyType, ValueType&gt; myMap; KeyType indicates the type of the key, while ValueType indicates the type of the value. When using std::unordered_map, [&hellip;]<\/p>\n","protected":false},"author":14,"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":[8237,7355,381,7370,12214],"class_list":["post-14204","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-c-data-structures","tag-c-map","tag-c-programming","tag-stdmap","tag-unordered_map"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>C++ Map Guide: std::map &amp; unordered_map - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn to implement mapping tables in C++ with std::map and unordered_map. 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