Question

I’m trying to count words occurrence in a string. For a string S, I need to show each word and how many times this word is present in the string.

Exemple:

string = ";! one two, tree foor one two !:;"

Result:

one: 2
two: 2
tree: 1
foor: 1

Here is my code but it’s not returning the right count:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int count_word(char * mot, char * text) {
  int n = 0;
  char *p;

  p = strstr(text, mot);

  while (p != NULL) {
    n++;
    p = strstr(p + 1, mot);
  }  

  return n;
}

void show_all_words(char * text) {
    char * p = strtok(text, " .,;-!?");

    while (p != NULL) {
      printf ("%s : %d\n", p, count_word(p, text));
      p = strtok(NULL, " .,;-!?");
    }
}

int main(char *argv[]) {

    char text[] = ";! one two, tree foor one two !:;";
    show_all_words(&text);

    return (EXIT_SUCCESS);
};

it’s returning:

one : 1
two : 0
tree : 0
foor : 0
one : 1
two : 0
: : 0

Answer 1

The function strtok changes its parameter. You can fix the problem by duplicating the string, calling strtok on one copy and count_word on the other.

Also, take a precaution not to output the count for the same word twice.

int count_word(char * mot, char * text, int offset) {
  int n = 0;
  char *p;

  p = strstr(text, mot);
  assert(p != NULL);
  if (p - text < offset)
      return -1; // if the word was found at an earlier offset, return an error code 

  while (p != NULL) {
    n++;
    p = strstr(p + 1, mot);
  }  

  return n;
}

void show_all_words(char * text) {
    char *text_rw = strdup(text); // make a read-write copy to use with strtok
    char * p = strtok(text_rw, " .,;-!?");

    while (p != NULL) {
      int offset = p - text; // offset of the word inside input text
      int count = count_word(p, text, offset);
      if (count != -1) // -1 is an error code that says "already looked at that word"
          printf ("%s : %d\n", p, count );
      p = strtok(NULL, " .,;-!?");
    }
    free(text_rw); // delete the copy
}