{"id":33620,"date":"2023-02-11T00:48:16","date_gmt":"2023-02-10T19:18:16","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-deciding-how-much-memory-to-dynamically-allocate-based-on-user-input\/"},"modified":"2023-02-11T00:48:16","modified_gmt":"2023-02-10T19:18:16","slug":"solved-deciding-how-much-memory-to-dynamically-allocate-based-on-user-input","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-deciding-how-much-memory-to-dynamically-allocate-based-on-user-input\/","title":{"rendered":"[Solved] Deciding how much memory to dynamically allocate based on user input"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-27783557\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"27783557\" data-parentid=\"27782806\" data-score=\"0\" 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>Here is a description of <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/www.cplusplus.com\/reference\/cstdlib\/malloc\/\"><code>malloc()<\/code><\/a>.<\/p>\n<p>It takes a parameter <code>size<\/code>, in bytes.<\/p>\n<p>So if the user entered 5 words, then you need to first allocate an array big enough to store 5 pointers.<\/p>\n<p>Eg.<\/p>\n<pre><code>char ** words = NULL;\nwords = malloc(sizeof(char *) * &lt;NUMBER OF CHARACTERS THE USER ENTERED&gt;);\n<\/code><\/pre>\n<p>If we assume ASCII is being used and a character is a char, then each letter in each of the words is a byte. We also need to account for any spaces, line feeds, perhaps a carriage return, and a trailing null.<\/p>\n<p>So how many letters are in a word? IDK, that&#8217;s up to you. But if we assume that <a rel=\"nofollow noopener\" target=\"_blank\" href=\"https:\/\/www.youtube.com\/watch?v=tRFHXMQP-QU\">&#8220;Supercalifragilisticexpialidocious&#8221; from Mary Poppins<\/a> in the longest word we will encounter, then we need to allocate at least 34 characters, plus an extra for a trailing null terminator. So that leaves us with up to 35 bytes per word.<\/p>\n<p>This will work:<\/p>\n<pre><code>enum { MAX_WORD_SIZE = sizeof(\"Supercalifragilisticexpialidocious\") };\n<\/code><\/pre>\n<p>This will also take into account the trailing <code>\\0<\/code> &#8211; MAX_WORD_SIZE will be 35.<\/p>\n<pre><code>char * temp_word = NULL;\ntemp_word = malloc(MAX_WORD_SIZE);\n<\/code><\/pre>\n<p>To create all of your other word arrays you&#8217;d need to do something similar in a loop:<\/p>\n<pre><code>for(int i = 0; i&lt; &lt;NUMBER OF WORDS THE USER ENTERED&gt;; i++)\n{\n    words[i] = malloc(MAX_WORD_SIZE);\n}\n<\/code><\/pre>\n<p>To convert the number of words entered by the user into an integer you should use <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/www.cplusplus.com\/reference\/cstdlib\/atoi\/?kw=atoi\"><code>atoi()<\/code><\/a><\/p>\n<p>After this you could use <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/www.cplusplus.com\/reference\/cstdio\/getchar\/\"><code>getchar()<\/code><\/a> to pull the string from stdin one character at a time and manually place them into temporary you allocated, stopping when you get to a <code>' '<\/code> space.<\/p>\n<p>To copy the temporary array into one of your word arrays you can use <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/www.cplusplus.com\/reference\/cstring\/strcpy\/?kw=strcpy\"><code>strcpy()<\/code><\/a>, just ensure your temporary array always has a trailig <code>\\0<\/code> after the word.<\/p>\n<p>Don&#8217;t forget to <code>free()<\/code> that pointer when you&#8217;re done.<\/p>\n<p>I am assuming you are doing this for some sort of a homework assignment on dynamic memory and that is why your application is defined the way it is. But if you aren&#8217;t you should consider just reading the input into one buffer first using <code>fgets()<\/code> and using <code>strtok()<\/code> to split the string after its been read. That approach will take more memory but it would be cleaner.<\/p>\n<p>Another thing you should consider doing is using <code>calloc()<\/code> instead of <code>malloc()<\/code> to do your allocation, that way you can ensure that all of your arrays are initialized with 0&#8217;s &#8211; it could save you from some confusion later on if there is garbage data already in those arrays.<\/p>\n<p>Yet another thing to think about: The temporary array in this example can be allocated automatically or statically using <code>temp_word[MAX_WORD_SIZE];<\/code> since I used an enum to store MAX_WORD_SIZE as a constant. There is no direct need to use malloc for this.<\/p>\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 Deciding how much memory to dynamically allocate based on user input <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] Here is a description of malloc(). It takes a parameter size, in bytes. So if the user entered 5 words, then you need to first allocate an array big enough to store 5 pointers. Eg. char ** words = NULL; words = malloc(sizeof(char *) * &lt;NUMBER OF CHARACTERS THE USER ENTERED&gt;); If we assume &#8230; <a title=\"[Solved] Deciding how much memory to dynamically allocate based on user input\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-deciding-how-much-memory-to-dynamically-allocate-based-on-user-input\/\" aria-label=\"More on [Solved] Deciding how much memory to dynamically allocate based on user input\">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":[324,712,362],"class_list":["post-33620","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-pointers","tag-string"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] Deciding how much memory to dynamically allocate based on user input - 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-deciding-how-much-memory-to-dynamically-allocate-based-on-user-input\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Deciding how much memory to dynamically allocate based on user input - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] Here is a description of malloc(). 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