Question

If this string compression code is given a string aaaabbbbcc, it will produce the string a4b4c2. However, the solution doesn’t work if the occurrence count of a character is greater than 9. What changes should be made?

void convert(char *s) {
    char *p = s;  
    char *q = s;  
    int c;
    int counter;
    while (*p) {
        c = *p;
        counter = 0;
        while (*p && *p == c) {
            p++;
            counter++;
        }
        *q++ = c; 
        *q++ = counter+'0'; 
    }
    *q = 0;
}

The issue is: there is no ASCII value for a number larger than 9. So, how to store that number in the string?

Answer 1

since these patterns do not normally occur in human readable form, I will deduce that it only needs to be machine readable, since 99.9% of words will have negative compression even if they have repeating chars

ex.
vaccuum -> v1a1c2u2m1

you don’t need to use int for a counter, you can simply use:

char c, counter=-128;

then you can just change

counter=0;
//to
counter=-128;

*q++ = counter+'0';
//to
*q++ = counter;

if you do need a human readable output use something like:

printf("%c,%d:",string[pos],(string[pos+1]+128));