{"id":10531,"date":"2022-09-24T00:54:04","date_gmt":"2022-09-23T19:24:04","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/"},"modified":"2022-09-24T00:54:04","modified_gmt":"2022-09-23T19:24:04","slug":"solved-vigenere-cipher-logic-error","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/","title":{"rendered":"[Solved] Vigenere Cipher logic error"},"content":{"rendered":"

[ad_1]
\n<\/p>\n

\n
\n
<\/div>\n
\n
\n

There are several problems with your code:<\/p>\n

You’re error checking isn’t correct. You check if(argc!=2||!apha)<\/code> after you’ve already evaluated strlen(argv[1])<\/code> — by then it’s too late! Check the validity of argc<\/code> before accessing argv<\/code> and don’t double up the argument count error and alphabetic key error, they’re independent. Also, error messages should go to stderr<\/code>, not stdout<\/code>.<\/p>\n

You’re completely mishandling the key indexing. As @Bob__ noted, the indexing in this code:<\/p>\n

if(isupper(key[i])){\n    k=key[j%keylength]-'A';\n}\n<\/code><\/pre>\n
needs to be consistent<\/p>\n
if (isupper(key[j % keylength])) {\n    k = key[j % keylength] - 'A';\n}\n<\/code><\/pre>\n
But also, you’re not incrementing j<\/code> correctly, you have it tracking i<\/code>:<\/p>\n
for (i=0,j=0;i<num;i++,j++){\n<\/code><\/pre>\n
Instead, i<\/code> should increment for every character in the input string, j<\/code> should increment for every encryptable letter in the input string.<\/p>\n
Reworking your code to fix the above errors and general style issues, we get something like:<\/p>\n
#include <stdio.h>\n#include <cs50.h>\n#include <ctype.h>\n#include <string.h>\n\nint main(int argc, string argv[]) {\n\n    if (argc != 2) {\n        fprintf(stderr, \"Please supply an encryption key.\\n\");\n        return 1;\n    }\n\n    string key = argv[1];\n    int key_length = strlen(key);\n    bool is_alpha = true;\n\n    for (int z = 0; z < key_length; z++) {\n        if (!isalpha(key[z])) {\n            is_alpha = false;\n        }\n    }\n\n    if (!is_alpha) {\n        fprintf(stderr, \"Sorry, we only accept alphabetic keys.\\n\");\n        return 1;\n    }\n\n    string in = GetString();\n    size_t length = strlen(in);\n\n    for (int i = 0, j = 0; i < length; i++) {\n\n        if (isalpha(in[i])) {\n\n            int ch, k = key[j++ % key_length];\n\n            if (isupper(k)) {\n                k -= 'A';\n            } else {\n                k -= 'a';\n            }\n\n            if (isupper(in[i])) {\n                int pos = in[i] - 'A';\n                ch = ((pos + k) % 26) + 'A';\n            } else {\n                int pos = in[i] - 'a';\n                ch = ((pos + k) % 26) + 'a';\n            }\n\n            printf(\"%c\", ch);\n        } else if (isspace(in[i])) {\n            printf(\" \");\n        } else if (ispunct(in[i])) {\n            printf(\"%c\", in[i]);\n        }\n    }\n\n    printf(\"\\n\");\n\n    return 0;\n}\n<\/code><\/pre>\n
USAGE SIMULATION<\/strong><\/p>\n
> .\/a.out baz\nworld, say hello!\nxoqmd, rby gflkp!\n>\n<\/code><\/pre>\n<\/p><\/div>\n
<\/div>\n<\/div>\n
            <\/span> <\/p><\/div>\n<\/div>\n
[ad_2]<\/p>\n
solved Vigenere Cipher logic error <\/p>\n","protected":false},"excerpt":{"rendered":"
[ad_1] There are several problems with your code: You’re error checking isn’t correct. You check if(argc!=2||!apha) after you’ve already evaluated strlen(argv[1]) — by then it’s too late! Check the validity of argc before accessing argv and don’t double up the argument count error and alphabetic key error, they’re independent. Also, error messages should go to … 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":[324,816,557,2899],"class_list":["post-10531","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-cs50","tag-encryption","tag-vigenere"],"yoast_head":"\n[Solved] Vigenere Cipher logic error - 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-vigenere-cipher-logic-error\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Vigenere Cipher logic error - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] There are several problems with your code: You’re error checking isn’t correct. You check if(argc!=2||!apha) after you’ve already evaluated strlen(argv[1]) — by then it’s too late! Check the validity of argc before accessing argv and don’t double up the argument count error and alphabetic key error, they’re independent. Also, error messages should go to ... Read more\" \/>\n<meta property=\"og:url\" content=\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/\" \/>\n<meta property=\"og:site_name\" content=\"JassWeb\" \/>\n<meta property=\"article:published_time\" content=\"2022-09-23T19:24:04+00:00\" \/>\n<meta name=\"author\" content=\"Kirat\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Kirat\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/\"},\"author\":{\"name\":\"Kirat\",\"@id\":\"https:\/\/jassweb.com\/solved\/#\/schema\/person\/65c9c7b7958150c0dc8371fa35dd7c31\"},\"headline\":\"[Solved] Vigenere Cipher logic error\",\"datePublished\":\"2022-09-23T19:24:04+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/\"},\"wordCount\":137,\"publisher\":{\"@id\":\"https:\/\/jassweb.com\/solved\/#organization\"},\"keywords\":[\"c++\",\"cs50\",\"encryption\",\"vigenere\"],\"articleSection\":[\"Solved\"],\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/\",\"url\":\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/\",\"name\":\"[Solved] Vigenere Cipher logic error - JassWeb\",\"isPartOf\":{\"@id\":\"https:\/\/jassweb.com\/solved\/#website\"},\"datePublished\":\"2022-09-23T19:24:04+00:00\",\"breadcrumb\":{\"@id\":\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/jassweb.com\/solved\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"[Solved] Vigenere Cipher logic error\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/jassweb.com\/solved\/#website\",\"url\":\"https:\/\/jassweb.com\/solved\/\",\"name\":\"JassWeb\",\"description\":\"Build High-quality Websites\",\"publisher\":{\"@id\":\"https:\/\/jassweb.com\/solved\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/jassweb.com\/solved\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/jassweb.com\/solved\/#organization\",\"name\":\"Jass Web\",\"url\":\"https:\/\/jassweb.com\/solved\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/jassweb.com\/solved\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/jassweb.com\/wp-content\/uploads\/2021\/02\/jass-website-logo-1.png\",\"contentUrl\":\"https:\/\/jassweb.com\/wp-content\/uploads\/2021\/02\/jass-website-logo-1.png\",\"width\":693,\"height\":132,\"caption\":\"Jass Web\"},\"image\":{\"@id\":\"https:\/\/jassweb.com\/solved\/#\/schema\/logo\/image\/\"}},{\"@type\":\"Person\",\"@id\":\"https:\/\/jassweb.com\/solved\/#\/schema\/person\/65c9c7b7958150c0dc8371fa35dd7c31\",\"name\":\"Kirat\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/jassweb.com\/solved\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/jassweb.com\/solved\/wp-content\/litespeed\/avatar\/1261af3c9451399fa1336d28b98ea3bb.jpg?ver=1775798750\",\"contentUrl\":\"https:\/\/jassweb.com\/solved\/wp-content\/litespeed\/avatar\/1261af3c9451399fa1336d28b98ea3bb.jpg?ver=1775798750\",\"caption\":\"Kirat\"},\"sameAs\":[\"http:\/\/jassweb.com\"],\"url\":\"https:\/\/jassweb.com\/solved\/author\/jaspritsinghghumangmail-com\/\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"[Solved] Vigenere Cipher logic error - JassWeb","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/","og_locale":"en_US","og_type":"article","og_title":"[Solved] Vigenere Cipher logic error - JassWeb","og_description":"[ad_1] There are several problems with your code: You’re error checking isn’t correct. You check if(argc!=2||!apha) after you’ve already evaluated strlen(argv[1]) — by then it’s too late! Check the validity of argc before accessing argv and don’t double up the argument count error and alphabetic key error, they’re independent. Also, error messages should go to ... Read more","og_url":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/","og_site_name":"JassWeb","article_published_time":"2022-09-23T19:24:04+00:00","author":"Kirat","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Kirat","Est. reading time":"2 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/#article","isPartOf":{"@id":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/"},"author":{"name":"Kirat","@id":"https:\/\/jassweb.com\/solved\/#\/schema\/person\/65c9c7b7958150c0dc8371fa35dd7c31"},"headline":"[Solved] Vigenere Cipher logic error","datePublished":"2022-09-23T19:24:04+00:00","mainEntityOfPage":{"@id":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/"},"wordCount":137,"publisher":{"@id":"https:\/\/jassweb.com\/solved\/#organization"},"keywords":["c++","cs50","encryption","vigenere"],"articleSection":["Solved"],"inLanguage":"en-US"},{"@type":"WebPage","@id":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/","url":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/","name":"[Solved] Vigenere Cipher logic error - JassWeb","isPartOf":{"@id":"https:\/\/jassweb.com\/solved\/#website"},"datePublished":"2022-09-23T19:24:04+00:00","breadcrumb":{"@id":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/jassweb.com\/solved\/solved-vigenere-cipher-logic-error\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/jassweb.com\/solved\/"},{"@type":"ListItem","position":2,"name":"[Solved] Vigenere Cipher logic error"}]},{"@type":"WebSite","@id":"https:\/\/jassweb.com\/solved\/#website","url":"https:\/\/jassweb.com\/solved\/","name":"JassWeb","description":"Build High-quality Websites","publisher":{"@id":"https:\/\/jassweb.com\/solved\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/jassweb.com\/solved\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/jassweb.com\/solved\/#organization","name":"Jass Web","url":"https:\/\/jassweb.com\/solved\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/jassweb.com\/solved\/#\/schema\/logo\/image\/","url":"https:\/\/jassweb.com\/wp-content\/uploads\/2021\/02\/jass-website-logo-1.png","contentUrl":"https:\/\/jassweb.com\/wp-content\/uploads\/2021\/02\/jass-website-logo-1.png","width":693,"height":132,"caption":"Jass Web"},"image":{"@id":"https:\/\/jassweb.com\/solved\/#\/schema\/logo\/image\/"}},{"@type":"Person","@id":"https:\/\/jassweb.com\/solved\/#\/schema\/person\/65c9c7b7958150c0dc8371fa35dd7c31","name":"Kirat","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/jassweb.com\/solved\/#\/schema\/person\/image\/","url":"https:\/\/jassweb.com\/solved\/wp-content\/litespeed\/avatar\/1261af3c9451399fa1336d28b98ea3bb.jpg?ver=1775798750","contentUrl":"https:\/\/jassweb.com\/solved\/wp-content\/litespeed\/avatar\/1261af3c9451399fa1336d28b98ea3bb.jpg?ver=1775798750","caption":"Kirat"},"sameAs":["http:\/\/jassweb.com"],"url":"https:\/\/jassweb.com\/solved\/author\/jaspritsinghghumangmail-com\/"}]}},"_links":{"self":[{"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/posts\/10531","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/comments?post=10531"}],"version-history":[{"count":0,"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/posts\/10531\/revisions"}],"wp:attachment":[{"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/media?parent=10531"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/categories?post=10531"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jassweb.com\/solved\/wp-json\/wp\/v2\/tags?post=10531"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}