{"id":19595,"date":"2022-11-07T05:00:45","date_gmt":"2022-11-06T23:30:45","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-how-to-read-an-input-from-a-file-one-at-a-time-similar-to-reading-input-from-console-using-cin-scanf-in-c\/"},"modified":"2022-11-07T05:00:45","modified_gmt":"2022-11-06T23:30:45","slug":"solved-how-to-read-an-input-from-a-file-one-at-a-time-similar-to-reading-input-from-console-using-cin-scanf-in-c","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-how-to-read-an-input-from-a-file-one-at-a-time-similar-to-reading-input-from-console-using-cin-scanf-in-c\/","title":{"rendered":"[Solved] How to read an input from a file one at a time similar to reading input from console using cin\/scanf in c++?"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-54174871\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"54174871\" data-parentid=\"54174445\" 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>As a first approximation, I&#8217;d make the most minimal changes necessary to the code that makes you happy:<\/p>\n<pre><code>std::ifstream infile(\"filename\");\n\nfor(int i = 0; i &lt;CLASS_SIZE; i++)\n{\n  for(int j = 0; j &lt;10 ; j++)\n    {          \n        \/\/ scanf(\"%d\", &amp;grade);\n        infile &gt;&gt; grade;\n        studentsInClass[i].setGrade(j,grade);\n    }  \n}\n<\/code><\/pre>\n<p>Given that you know the exact number of grades for each student, you gain little (if anything) from using <code>getline<\/code>. That would be useful primarily if the input was line-oriented. For example, consider an input file like this:<\/p>\n<pre><code>91 92 85 58 87 75 89 97 79 65 88 \n72 81 94 90 61 72 75 68 77\n75 49 87 79 65 64 62 51 44 70\n<\/code><\/pre>\n<p>As it stands, you still apparently want this read as 3 students with 10 grades apiece, so the last grade on the first line (the <code>88<\/code>) belongs to the second student, not the first.<\/p>\n<p>Using <code>getline<\/code> and then parsing each line individually would make sense if you wanted this input data interpreted as the first student having 11 grades, and the second student 9 grades (and the third 10 grades).<\/p>\n<hr>\n<p>That covers the question you asked, but I&#8217;m still not particularly happy about the code. Personally, I&#8217;d prefer to write a student class that knew how to read its own data from a stream:<\/p>\n<pre><code>class student { \n    std::vector&lt;int&gt; grades;\npublic:\n\n   \/\/ other stuff, of course.\n\n   friend std::istream &amp;operator&gt;&gt;(std::istream &amp;is, student &amp;s) {\n       int grade;\n       for (int i=0; i&lt;10; i++) {\n           is &gt;&gt; grade;\n           s.grades.push_back(grade);\n       }\n       return is;\n    }\n};\n<\/code><\/pre>\n<p>Then when we want to read data for multiple students, we&#8217;d do something like this:<\/p>\n<pre><code>std::vector&lt;students&gt; the_class;\nstd::ifstream infile(\"grades.txt\");\n\nfor (int i=0; i&lt;CLASS_SIZE; i++) {\n    student s;\n\n    \/\/ use `operator&gt;&gt;` above to read all 10 grades for one student.\n    infile &gt;&gt; s;\n    the_class.push_back(s);\n}\n<\/code><\/pre>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\"><\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved How to read an input from a file one at a time similar to reading input from console using cin\/scanf in c++? <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] As a first approximation, I&#8217;d make the most minimal changes necessary to the code that makes you happy: std::ifstream infile(&#8220;filename&#8221;); for(int i = 0; i &lt;CLASS_SIZE; i++) { for(int j = 0; j &lt;10 ; j++) { \/\/ scanf(&#8220;%d&#8221;, &amp;grade); infile &gt;&gt; grade; studentsInClass[i].setGrade(j,grade); } } Given that you know the exact number of &#8230; <a title=\"[Solved] How to read an input from a file one at a time similar to reading input from console using cin\/scanf in c++?\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-how-to-read-an-input-from-a-file-one-at-a-time-similar-to-reading-input-from-console-using-cin-scanf-in-c\/\" aria-label=\"More on [Solved] How to read an input from a file one at a time similar to reading input from console using cin\/scanf in c++?\">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":[324,513],"class_list":["post-19595","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-c11"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] How to read an input from a file one at a time similar to reading input from console using cin\/scanf in c++? - 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-to-read-an-input-from-a-file-one-at-a-time-similar-to-reading-input-from-console-using-cin-scanf-in-c\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] How to read an input from a file one at a time similar to reading input from console using cin\/scanf in c++? - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] As a first approximation, I&#8217;d make the most minimal changes necessary to the code that makes you happy: std::ifstream infile(&quot;filename&quot;); for(int i = 0; i &lt;CLASS_SIZE; i++) { for(int j = 0; j &lt;10 ; j++) { \/\/ scanf(&quot;%d&quot;, &amp;grade); infile &gt;&gt; grade; studentsInClass[i].setGrade(j,grade); } } Given that you know the exact number of ... 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