{"id":12734,"date":"2022-10-01T17:51:15","date_gmt":"2022-10-01T12:21:15","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-how-do-i-print-a-vector-of-arrays-lists-using-int-iterator-in-cpp\/"},"modified":"2022-10-01T17:51:15","modified_gmt":"2022-10-01T12:21:15","slug":"solved-how-do-i-print-a-vector-of-arrays-lists-using-int-iterator-in-cpp","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-how-do-i-print-a-vector-of-arrays-lists-using-int-iterator-in-cpp\/","title":{"rendered":"[Solved] how do i print a vector of arrays\/lists using int iterator in cpp?"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-48479382\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"48479382\" data-parentid=\"48478863\" data-score=\"1\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>You can&#8217;t iterate through a list with an integer, but you can declare <code>j<\/code> as an iterator (<code>std::list&lt;int&gt;::iterator j = adjList[i].begin();<\/code>) and use the asterisk like in pointers to get the element that an iterator is pointing at like this: <code>cout &lt;&lt; *j &lt;&lt; ' ';<\/code>. If you want to print a vector of arrays, just do it like how you would normally print a 2D array. The <code>std::list<\/code> container implements a linked list and is very different from containers that store elements in contiguous memory such as arrays and <code>std::vector<\/code>, which is likely not what you want here since it doesn&#8217;t have random access.<\/p>\n<p>By the way, if you want to pass large containers like vectors to a function like <code>print()<\/code> that does not need to modify the vector, you should use a <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/www.cplusplus.com\/doc\/tutorial\/functions\/\">constant reference<\/a> instead of copying the vector. There is something called a <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/www.cplusplus.com\/doc\/tutorial\/control\/\">range based for loop<\/a> in C++11 that can iterate through things like vectors without you having to worry about things like iterators, and a <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/www.cplusplus.com\/reference\/set\/set\/?kw=set\"><code>std::set<\/code><\/a> is probably more suited for implementing an adjacency list since it allows for checking if two vertices are adjacent with logarithmic complexity.<\/p>\n<p>Lastly, in your input loop, you used <code>adjList[u]<\/code> when that element does not exist yet since <code>adjList<\/code> is empty. You should add a line <code>adjList.resize(n)<\/code> after you input n to create the empty sets or just declare <code>adjList<\/code> after you input <code>n<\/code> and use <code>n<\/code> as the constructor argument like this to tell the constructor to initialize <code>adjList<\/code> with a bunch of empty sets: <code>vector&lt;set&lt;int&gt;&gt; adjList(n);<\/code>.<\/p>\n<p>Since it looks like you are doing a competitive programming problem, I would advise you to convert the input to zero indexing before doing any processing.<\/p>\n<p>My code using range based for loops:<\/p>\n<pre><code>#include &lt;iostream&gt;\n#include &lt;vector&gt;\n#include &lt;set&gt;\n\nvoid print(const std::vector&lt;std::set&lt;int&gt;&gt; &amp;adjList)\/\/pass by const reference\n{\n    for(std::size_t i = 0; i &lt; adjList.size(); i++)\n    {\n        std::cout &lt;&lt; i &lt;&lt; \": \";\n        for(auto &amp;j : adjList[i])\/\/range based for loop to iterate through adjList[i] and use the reference j to refer to each element\n        {\n            std::cout &lt;&lt; j &lt;&lt; ' ';\n        }\n        std::cout &lt;&lt; '\\n';\n    }\n}\n\nint main()\n{\n    int n, m;\n    std::cin &gt;&gt; n &gt;&gt; m;\n    std::vector&lt;std::set&lt;int&gt;&gt; adjList(n); \/\/adjList starts with n empty sets\n    for(int i = 0; i &lt; m; i++)\n    {\n        int u, v;\n        std::cin &gt;&gt; u &gt;&gt; v;\n        adjList[u].insert(v);\n        adjList[v].insert(u);\n    }\n    print(adjList);\n}\n<\/code><\/pre>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">0<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved how do i print a vector of arrays\/lists using int iterator in cpp? <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] You can&#8217;t iterate through a list with an integer, but you can declare j as an iterator (std::list&lt;int&gt;::iterator j = adjList[i].begin();) and use the asterisk like in pointers to get the element that an iterator is pointing at like this: cout &lt;&lt; *j &lt;&lt; &#8216; &#8216;;. If you want to print a vector of &#8230; <a title=\"[Solved] how do i print a vector of arrays\/lists using int iterator in cpp?\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-how-do-i-print-a-vector-of-arrays-lists-using-int-iterator-in-cpp\/\" aria-label=\"More on [Solved] how do i print a vector of arrays\/lists using int iterator in cpp?\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[324],"class_list":["post-12734","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] how do i print a vector of arrays\/lists using int iterator in cpp? - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-how-do-i-print-a-vector-of-arrays-lists-using-int-iterator-in-cpp\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] how do i print a vector of arrays\/lists using int iterator in cpp? - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] You can&#8217;t iterate through a list with an integer, but you can declare j as an iterator (std::list&lt;int&gt;::iterator j = adjList[i].begin();) and use the asterisk like in pointers to get the element that an iterator is pointing at like this: cout &lt;&lt; *j &lt;&lt; &#039; &#039;;. 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