palindromes in a string

[997.2]

Hi
I'm trying to finish up this program but it won't work and I don't see what I'm doing wrong ...

I have a string input from the user, I'll use string tokenization to split the sentence into words

#include <string.h>
#include <stdio.h>
#define SIZE 80
int check(char string[], int size);
int main() {
    char a[SIZE];
    int count=0, l;
    char delims[] = " ";
    char *token;

    printf("Enter a sentence to check for palindromes\n> ");
    gets(a);
    token = strtok(a,delims);
    
    while(token != NULL) {
                l=strlen(token)-1;
                puts(token);
                token = strtok(NULL, delims);
                if(check(token,l) == 1)
                                  count++;
                                       }
    printf("Number of palindroms is: %d\n", count);
    system("pause");
    return 0;
}
int check(char string[], int size) {
    int i,flag=0;
    char temp[size];
    if(size <= 1)
            return 0;

   for(i=0;i<size;i++)
   string[i] = tolower(string[i]);
   strcpy(temp,string);
   strrev(temp);
   if(strcmp(string,temp)==0)
         return 1;
    
}
}

Thank you

[oogabooga]

Your spacing is uneven. You have an extra brace at the end.

l is a bad variable name since it looks like a 1. Try len. (Although why doesn't check do it's own strlen call if it needs the length?)

Your main error is that you've placed the call to strtok that's in the loop in the wrong position. It should be the last statement in the loop body.

You also need a return 0 at the end of check. Otherwise, what happens if strcmp doesn't return zero?

Overall, it seems a pretty inefficient implementation. You don't actually need another copy of the string.

[997.2]

Thank you very much!! that solved my problem!
but can you explain to me how to do it without copying the string?

[oogabooga]

The idea is to have two pointers (or indices), one starting at the beginning of the string and the other at the end. While the two indicated chars are the same, move the pointers/indices towards each other (increment the low one, decrement the high one) and check again. If you find different chars, return 0 (false); if the pointers/indices "meet in the middle", return 1 (true).