Question

Is there in C language a way to do something like:

/* it's a demo code. I know that it doesn't work. */
char foo[] = "abc";
char* p = &foo[0];
int len = 3;

while(len) {
    printf("%c", *p);
    p--;
    len--;
}

and get cba output?

My question is: there any simple way to do this? maybe using arithmetic pointers. I know that I can write an function-like:

/* Note: I haven't tested the this code. But I believe that works. */
char *strrev(char input[]) {
    if (input == NULL) return NULL;

    int len = strlen(input) - 1;
    char * rev = malloc(len+1);

    if (rev == NULL) return NULL;

    for (; len != 0; len--) *rev++ = input[len];

    if (len == 0) {
      *rev++= '\0';
       return rev;
    } else {
       free(rev);     
       return NULL;
    }   
}

But I’m looking for more simple way, I need write a function that starts the comparisons from half string.

Answer 1

void backwards_print(const char *text) {
    /* don't even try to print an empty string */
    if (*text) {
        const char *p = text;

        /* go to the end */
        while (*p++) /* void */;

        /* print from the end */
        while (p != text) putchar(*--p);

    }
    putchar('\n'); /* newline, flush buffer */
}

Example usage

char foo[] = "abc";
backwards_print(foo);