Tokenize Strings using Pointers in ANSI C

Question

This is in Ansi C. I am given a string. I am supposed to create a method that returns an array of character pointers that point to the beginning of each word of said string. I am not allowed to use Malloc, but instead told that the maximum length of input will be 80.

Also, before anyone flames me for not searching the forum, I can't use strtok :(

char input[80] = "hello world, please tokenize this string"

and the output of the method should have 6 elements;

output[0] points to the "h",
output[1] points to the "w",

and so on.

How should I write the method?

Also, I need a similar method to handle input from a file with maximum of 110 lines.

Answer 1

Pseudocode:

boolean isInWord = false
while (*ptr != NUL character) {
   if (!isInWord and isWordCharacter(*ptr)) {
       isInWord = true
       save ptr
   } else if (isInWord and !isWordCharacter(*ptr)) {
       isInWord = false
   }
   increment ptr
}

isWordCharacter checks whether the character is part of the word or not. Depending on your definition, it can be only alphabet character (recognize part-time as 2 words), or it may include - (recognize part-time as one word).

Answer 2

Because it's homework here's a part of what you might need:

char* readPtr = input;
char* wordPtr = input;
int wordCount = 0;
while (*readPtr++ != ' ');
/* Here we have a word from wordPtr to readPtr-1 */
output[wordCount++] = /* something... :)  */

You'll need that in a loop, and must consider how to move onto the next word, and check for end of input.