נושא: עזרה דחופה

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

#define MAX_LEN 100


/*
 * This function replaces the occurances of 'sub' in 'src' with the
 * string 'repl'.
 * assumption: length of 'repl' smaller or equal to the length of 'sub'
 */
void str_replace(char *src, char *sub, char *repl) {

    char *ptr1, *ptr2; /* two pointers for going over the input string */
    
    int repl_len = strlen(repl),
        sub_len = strlen(sub);
    int diff = sub_len - repl_len;

    /* loop over all instances of string to replace */
    ptr1 = strstr(src, sub);
    while (ptr1 != NULL)
    {
        /* copy replacing string into string.
        /* we use strncpy in order not to copy the terminator '\0' */
        strncpy(ptr1, repl, repl_len);

       
        /* increment both pointers,
         * ptr1 points to the string after the replacement
         * ptr2 points to the string after the substituted part
         * (which may be longer) */
        ptr2 = ptr1 + sub_len;
        ptr1 += repl_len;

        /* this loop moves characters backwards,
         * if the replaced string was shorter than the original part */
        while ((*ptr2) != '\0')
        {
            *(ptr2-diff) = (*ptr2);
            ptr2++;
        }
        *(ptr2 - diff) = '\0';

        /* get next instance */
        ptr1 = strstr(ptr1, sub);
    }
}


/*
 * Read a string from the user until the end of the line.
 * read no more than size characters and ignore the rest.
 */
void getline(char *arr, int size)
{
    int counter = 0;
    char c = getchar();

    while (c != '\n')
    {
        if (counter < size)
        {
            *arr = c;
            arr++;
        }
        counter++;
        c = getchar();
    }

    *arr = '\0';
}


int main(int argc, char* argv[]) {

    char src[MAX_LEN + 1];
    char sub[MAX_LEN + 1];
    char repl[MAX_LEN + 1];

    printf("Please enter a string: ");
    getline(src, MAX_LEN);
    printf("Please enter a part to substitute: ");
    getline(sub, MAX_LEN);
    printf("Please enter the replacement: ");
    getline(repl, MAX_LEN);

    /* make sure none of the strings is empty */
    if (*src == '\0'  ||  *sub == '\0'  ||  *repl == '\0') {
        printf("Empty string. Please check your input.\n");
        return 1;
    }

    /* make sure the replacment is not longer than the substituted string */
    if (strlen(sub) < strlen(repl)) {
        printf("replacement substring should not be longer than the replaced substring\n");
        return 1;
    }

    str_replace(src, sub, repl);
    printf("after replacement: %s\n", src);getch();
}
// End Of File