{"id":30734,"date":"2023-01-17T01:25:58","date_gmt":"2023-01-16T19:55:58","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-extracting-power-from-polynomials\/"},"modified":"2023-01-17T01:25:58","modified_gmt":"2023-01-16T19:55:58","slug":"solved-extracting-power-from-polynomials","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-extracting-power-from-polynomials\/","title":{"rendered":"[Solved] extracting power from polynomials"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-29431335\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"29431335\" data-parentid=\"29431102\" 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>Problems:<\/p>\n<ol>\n<li>\n<p>If the user enters something that doesn&#8217;t contain a <code>'^'<\/code>, then your code exhibits <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/en.wikipedia.org\/wiki\/Undefined_behavior\">Undefined Behavior<\/a> as num is not initialized here<\/p>\n<pre><code>if(isdigit(num))\n<\/code><\/pre>\n<p>If the input does contain a <code>'^'<\/code>, then the <code>if<\/code> will be true.<\/p>\n<\/li>\n<li>\n<p>Here:<\/p>\n<pre><code>strcat(power,parts[k]);\n<\/code><\/pre>\n<p><code>strcat<\/code> finds the NUL-terminator in its first argument and overwrites its second argument from that position. But <code>power<\/code> isn&#8217;t initialized! So, this also invokes <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/en.wikipedia.org\/wiki\/Undefined_behavior\">Undefined Behavior<\/a>. Furthermore, <code>parts[k]<\/code> is a <code>char<\/code>, but <code>strcat<\/code> expects both its arguments to be NUL-terminated and <strong>be of type <code>const char*<\/code><\/strong>.<br \/>\nInitialize `power by using <\/p>\n<pre><code>char power[30]={0};\n<\/code><\/pre>\n<p>and change the <code>strcat<\/code> to<\/p>\n<pre><code>strcat(power,&amp;parts[k]);\n<\/code><\/pre>\n<\/li>\n<li>\n<p>The same problem is seen here too:<\/p>\n<pre><code>strcpy(power,'1');\n<\/code><\/pre>\n<p>Change it to <\/p>\n<pre><code>strcpy(power,\"1\");\n<\/code><\/pre>\n<p>to fix it. The double quotes make the string literal of type <code>const char*<\/code> which is <code>\\0<\/code> terminated<\/p>\n<\/li>\n<li>\n<p>Here:<\/p>\n<pre><code>scanf(\"%s\",parts);\n<\/code><\/pre>\n<p>The user <em>could<\/em> enter some string more than 29 characters long(+1 for the <code>\\0<\/code> terminator). This would also cause <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/en.wikipedia.org\/wiki\/Undefined_behavior\">Undefined Behavior<\/a>. Fix it by limiting the number of characters to be scanned by using<\/p>\n<pre><code>scanf(\"%29s\",parts);\n<\/code><\/pre>\n<p>The <code>scanf<\/code> will scan at most 29 characters(+1 for the <code>\\0<\/code> terminator) from the standard input stream when this is done.<\/p>\n<\/li>\n<\/ol>\n<\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">6<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved extracting power from polynomials <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] Problems: If the user enters something that doesn&#8217;t contain a &#8216;^&#8217;, then your code exhibits Undefined Behavior as num is not initialized here if(isdigit(num)) If the input does contain a &#8216;^&#8217;, then the if will be true. Here: strcat(power,parts[k]); strcat finds the NUL-terminator in its first argument and overwrites its second argument from that &#8230; <a title=\"[Solved] extracting power from polynomials\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-extracting-power-from-polynomials\/\" aria-label=\"More on [Solved] extracting power from polynomials\">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-30734","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] extracting power from polynomials - 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-extracting-power-from-polynomials\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] extracting power from polynomials - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] Problems: If the user enters something that doesn&#8217;t contain a &#039;^&#039;, then your code exhibits Undefined Behavior as num is not initialized here if(isdigit(num)) If the input does contain a &#039;^&#039;, then the if will be true. 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