{"id":13539,"date":"2024-03-15T07:20:35","date_gmt":"2024-03-15T07:20:35","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-do-you-change-the-value-of-an-element-in-a-vector-in-c\/"},"modified":"2025-08-05T19:55:33","modified_gmt":"2025-08-05T19:55:33","slug":"how-do-you-change-the-value-of-an-element-in-a-vector-in-c","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-do-you-change-the-value-of-an-element-in-a-vector-in-c\/","title":{"rendered":"Change Vector Element Value in C++"},"content":{"rendered":"<p>In C++, you can use the square brackets operator or the at() function to modify the elements in a vector. Here are examples of both methods:<\/p>\n<ol>\n<li>I stumbled upon an old friend at the grocery store.<\/li>\n<\/ol>\n<pre class=\"post-pre\"><code><span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;iostream&gt;<\/span><\/span>\r\n<span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;vector&gt;<\/span><\/span>\r\n\r\n<span class=\"hljs-function\"><span class=\"hljs-type\">int<\/span> <span class=\"hljs-title\">main<\/span><span class=\"hljs-params\">()<\/span> <\/span>{\r\n    std::vector&lt;<span class=\"hljs-type\">int<\/span>&gt; vec = {<span class=\"hljs-number\">1<\/span>, <span class=\"hljs-number\">2<\/span>, <span class=\"hljs-number\">3<\/span>, <span class=\"hljs-number\">4<\/span>, <span class=\"hljs-number\">5<\/span>};\r\n\r\n    <span class=\"hljs-comment\">\/\/ \u4fee\u6539vector\u4e2d\u7684\u7b2c3\u4e2a\u5143\u7d20<\/span>\r\n    vec[<span class=\"hljs-number\">2<\/span>] = <span class=\"hljs-number\">10<\/span>;\r\n\r\n    <span class=\"hljs-comment\">\/\/ \u8f93\u51fa\u4fee\u6539\u540e\u7684vector<\/span>\r\n    <span class=\"hljs-keyword\">for<\/span> (<span class=\"hljs-type\">int<\/span> i = <span class=\"hljs-number\">0<\/span>; i &lt; vec.<span class=\"hljs-built_in\">size<\/span>(); i++) {\r\n        std::cout &lt;&lt; vec[i] &lt;&lt; <span class=\"hljs-string\">\" \"<\/span>;\r\n    }\r\n    std::cout &lt;&lt; std::endl;\r\n\r\n    <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">0<\/span>;\r\n}\r\n<\/code><\/pre>\n<p>Output: Generate\/produce\/result in<\/p>\n<pre class=\"post-pre\"><code>1 2 10 4 5\r\n<\/code><\/pre>\n<ol>\n<li>I am currently working on it.<\/li>\n<\/ol>\n<pre class=\"post-pre\"><code><span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;iostream&gt;<\/span><\/span>\r\n<span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;vector&gt;<\/span><\/span>\r\n\r\n<span class=\"hljs-function\"><span class=\"hljs-type\">int<\/span> <span class=\"hljs-title\">main<\/span><span class=\"hljs-params\">()<\/span> <\/span>{\r\n    std::vector&lt;<span class=\"hljs-type\">int<\/span>&gt; vec = {<span class=\"hljs-number\">1<\/span>, <span class=\"hljs-number\">2<\/span>, <span class=\"hljs-number\">3<\/span>, <span class=\"hljs-number\">4<\/span>, <span class=\"hljs-number\">5<\/span>};\r\n\r\n    <span class=\"hljs-comment\">\/\/ \u4fee\u6539vector\u4e2d\u7684\u7b2c4\u4e2a\u5143\u7d20<\/span>\r\n    vec.<span class=\"hljs-built_in\">at<\/span>(<span class=\"hljs-number\">3<\/span>) = <span class=\"hljs-number\">20<\/span>;\r\n\r\n    <span class=\"hljs-comment\">\/\/ \u8f93\u51fa\u4fee\u6539\u540e\u7684vector<\/span>\r\n    <span class=\"hljs-keyword\">for<\/span> (<span class=\"hljs-type\">int<\/span> i = <span class=\"hljs-number\">0<\/span>; i &lt; vec.<span class=\"hljs-built_in\">size<\/span>(); i++) {\r\n        std::cout &lt;&lt; vec.<span class=\"hljs-built_in\">at<\/span>(i) &lt;&lt; <span class=\"hljs-string\">\" \"<\/span>;\r\n    }\r\n    std::cout &lt;&lt; std::endl;\r\n\r\n    <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">0<\/span>;\r\n}\r\n<\/code><\/pre>\n<p>output:<\/p>\n<pre class=\"post-pre\"><code>1 2 3 20 5\r\n<\/code><\/pre>\n<p>Both the [] operator and the at() function can be used to directly modify the elements in a vector based on their index. It is important to note that indexing starts at 0. When using the [] operator, accessing elements beyond the vector&#8217;s range may result in undefined behavior, whereas using the at() function will throw a std::out_of_range exception.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In C++, you can use the square brackets operator or the at() function to modify the elements in a vector. Here are examples of both methods: I stumbled upon an old friend at the grocery store. #include &lt;iostream&gt; #include &lt;vector&gt; int main() { std::vector&lt;int&gt; vec = {1, 2, 3, 4, 5}; \/\/ \u4fee\u6539vector\u4e2d\u7684\u7b2c3\u4e2a\u5143\u7d20 vec[2] = [&hellip;]<\/p>\n","protected":false},"author":12,"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":[381,3693,18058,18059,5117],"class_list":["post-13539","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-c-programming","tag-c-vectors","tag-modify-vector-elements","tag-stl-vectors","tag-vector-operations"],"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>Change Vector Element Value in C++ - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn how to modify vector elements in C++ using bracket operators or at() function. 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