Multidimensional string arrays and comparing characters

**ArcadeEdge** · 02-15-2012

I'm trying to read in a file and find words that ONLY contain certain characters. For example, I want to find words that only have "ats" so "bats" or "cats" would be invalid but "ats", "stats", "sat" would be valid.

So far I've gotten my program to count how many times the characters m e l o w show up, which for my test is 37. For my test text file I have

hello
low
meow
mole
owl
dog
paper
cat
books
marshmellow
pillow
moles

Code:

int main(void) {

   char TEST[5] = {'m', 'e', 'l', 'o', 'w'};

   int max_words=12;
   int max_len=12;
   int i,k,j,letter=0, t=0;
   char words[max_words][max_len];

   FILE *in = NULL;   
   in = fopen("dummy.txt", "r"); //opens file for reading

   //verify that file is open
   if (in == NULL) 
      printf("Unable to open input file.");

   //read data
   for(i=0; !feof(in) && i<max_words ;i++) {
      fscanf(in, "%s", &words[i][max_len]);
      printf("%s\n", &words[i][max_len]);

   }
   
   //print out characters
   printf("\n");
   for(j=1; j<=max_words; j++) {
      for(k=0;k<max_len;k++) {
         if(words[j][k]!='\0'){
            printf("%c.", words[j][k]);
         }
         else
            break;
         for(t=0;t<5;t++) { //count the number of times the character shows up
         if(words[j][k]==TEST[t])
            letter++;
         }
      }
   printf("\n");
   }

   printf("\n=i%d. k=%d letter=%d", i, k, letter);

   return 0;  
}

**dmh2000** · 02-15-2012

not sure what your question is, but one thing i see in your first loop reading in the data,

&words[i][max_len]

this is going to offset your data by i+1 in the array. your words[0] element will be empty. i think you want to use '&words][i][0]' or just 'words[i]' when reading the data in. that's why you had to use j=1;j<= max_words in your print loop.

if your question is how to actually know if the word is valid, it seems that if you set letter = 0 before your loop over the characters in a word ('for(k=...') then after that loop check if 'letter == strlen(word[j])' that would tell you if there were no invalid characters in that word.

**ArcadeEdge** · 02-15-2012

Originally Posted by dmh2000

not sure what your question is, but one thing i see in your first loop reading in the data,

&words[i][max_len]

this is going to offset your data by i+1 in the array. your words[0] element will be empty. i think you want to use '&words][i][0]' or just 'words[i]' when reading the data in. that's why you had to use j=1;j<= max_words in your print loop.

if your question is how to actually know if the word is valid, it seems that if you set letter = 0 before your loop over the characters in a word ('for(k=...') then after that loop check if 'letter == strlen(word[j])' that would tell you if there were no invalid characters in that word.

Thank you! Your solution works perfectly!
I was over thinking it, thinking I had to compare each character and if doesn't match, throw away the word.

**ArcadeEdge** · 02-15-2012

I have another question.

What if I wanted to check for capital letters too?
Can I subtract 32 (dec) from each element in TEST? So I will get the capital letter ascii value?

for example:

Code:

for(t=0;t<5;t++) {
   if(words[j][k]==TEST[t] || words[j][k]==TEST[t]-32)
   ..code...
}

**anduril462** · 02-15-2012

Originally Posted by ArcadeEdge

What if I wanted to check for capital letters too?
Can I subtract 32 (dec) from each element in TEST? So I will get the capital letter ascii value?

You could, but that's the worst way to do it. First off, 32 is a "magic number". It's cryptic and nobody looking at your code would know what you're doing there, without considerable research. You would be better off using test[t] - ('a' - 'A'), but that's still far from ideal. Subtracting 32 is specific to ASCII, so your application wouldn't work for systems that use, say, EBCDIC. The best solution would be to use the toupper/tolower functions provided by ctype.h:

Code:

if (toupper(words[j][k]) == toupper(TEST[t]))
    ...

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