{"id":6653,"date":"2024-11-09T00:01:14","date_gmt":"2024-11-09T08:01:14","guid":{"rendered":"https:\/\/c-for-dummies.com\/blog\/?p=6653"},"modified":"2024-11-16T09:22:41","modified_gmt":"2024-11-16T17:22:41","slug":"hexwords","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=6653","title":{"rendered":"HexWords"},"content":{"rendered":"

Hexadecimal, or counting base 16, uses letters A through F to represent values 11 through 15. This base — “hex” — is common in programming as it works as a shorthand for binary values. But the letters used are also letters, which means that they can spell words.
\n
\nA recent challenge on Rosetta Code<\/a> is to use a digital dictionary to find all hex words with four or more letters. These are words like FACE or CAFE, which are hex values 64,236 and 51,966, respectively.<\/p>\n

The challenge went on to order the results and perform other magic, but it got me curious.<\/p>\n

Last year I wrote a series<\/a> about accessing the Linux dictionary file and then plundering it for various words. I can use the same techniques to find hexwords, or those words in the electronic dictionary that are composed only of letters A through F.<\/p>\n

I approach this problem in two steps.<\/p>\n

First read every word in the digital dictionary. It’s found at \/usr\/share\/dict\/words<\/code> for most Linux configurations.<\/p>\n

Second, scan each found word for matches with the letters A through F, both upper- and lowercase. This part may seem like a lot of work, but the scanf()<\/em> function has a special mode that finds only specific letters. I wrote about this letter filter<\/a> several years ago.<\/p>\n

Here is my code, which outputs all hexwords found in the Linux dictionary:<\/p>\n

2024_11_09-Lesson.c<\/a><\/h3>\n
\r\n\/* Hex Words *\/<\/span>\r\n#include <stdio.h>\r\n#include <stdlib.h>\r\n#include <string.h>\r\n\r\n\/* this code assumes the following path is valid *\/<\/span>\r\n#define DICTIONARY \"\/usr\/share\/dict\/words\"\r\n#define SIZE 32\r\n\r\nint main()\r\n{\r\n    FILE *dict;\r\n    char word[SIZE],hexword[SIZE],*r,*w;\r\n\r\n    \/* open the dictionary *\/<\/span>\r\n    dict = fopen(DICTIONARY,\"r\");\r\n    if( dict==NULL )\r\n    {\r\n        fprintf(stderr,\"Unable to open %s\\n\",DICTIONARY);\r\n        exit(1);\r\n    }\r\n\r\n    \/* read the dictionary *\/<\/span>\r\n    while( !feof(dict) )\r\n    {\r\n        \/* read a word from the dictionary *\/<\/span>\r\n        r = fgets(word,SIZE,dict);\r\n        if( r==NULL )    \/* no word, done *\/<\/span>\r\n            break;\r\n\r\n        \/* remove newline *\/<\/span>\r\n        w = word;\r\n        while(*w)\r\n        {\r\n            if( *w=='\\n' )\r\n            {\r\n                *w = '\\0';\r\n                break;\r\n            }\r\n            w++;\r\n        }\r\n\r\n        \/* pull out only hex characters *\/<\/span>\r\n        sscanf(word,\"%[ABCDEFabcdef]\",hexword);\r\n\r\n        \/* compare hexword with original word *\/<\/span>\r\n        if( strcmp(word,hexword)==0 )\r\n            printf(\"%s\\n\",hexword);\r\n    }\r\n\r\n\r\n    \/* clean-up *\/<\/span>\r\n    fclose(dict);\r\n    return(0);\r\n}<\/pre>\n
The code’s while<\/em> loop is stolen directly from the earlier post, which scans all words in the dictionary. The found word is stored in buffer word[]<\/code>. An inner while<\/em> loop replaces the newline (read by the fgets()<\/em> function) with a null character, which makes for better matching later in the code.<\/p>\n
The sscanf()<\/code> function scans the dictionary word and returns only the portion that contains upper- and lowercase letters A through F.<\/p>\n
sscanf(word,\"%[ABCDEFabcdef]\",hexword);<\/code><\/p>\n
This result is saved in buffer hexword[]<\/code>. If both word[]<\/code> and hexword[]<\/code> match (the result of the strcmp()<\/em> function is zero), a true hexword is found. A printf()<\/em> statement outputs the results.<\/p>\n
A sample run of the program generates 120 positive hits. Here’s a snapshot of the output:<\/p>\n
A
\nAA
\nAAA
\nAB
\nABC
\nAC
\nAF
\nAFC
\n...
\nfacade
\nface
\nfaced
\nfad
\nfade
\nfaded
\nfed
\nfee
\nfeed<\/code><\/p>\n
The original Rosetta Code challenge limited output to words four characters long or greater. The code above apply this restriction, which I add next week<\/a>, along with other updates to sate my inner nerd.<\/p>\n","protected":false},"excerpt":{"rendered":"
How many words in the dictionary can be written by using hexadecimal “digits” A through F? Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-6653","post","type-post","status-publish","format-standard","hentry","category-main"],"_links":{"self":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6653","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6653"}],"version-history":[{"count":5,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6653\/revisions"}],"predecessor-version":[{"id":6696,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6653\/revisions\/6696"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6653"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6653"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6653"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}