Question

I was writing a program where I have to remove all the consecutive repeated occurance of a sub-string in increasing order of length starting at 1.

For example if string is “abcabeccced”.
After removing repeated sub-string of length 1: “abcababceccced” –> “abcababceced” (2 ‘c’ are removed)
After removing repeated sub-string of length 2: “abcababceced” –> “abcabceced” (substring “ab” is removed)
and so on…

Can someone suggest an efficient code for this or even a idea how to do it?

Answer 1

This is untested pseudo code, but you’re looking to do something like this:

 void crunch(char *str)
 {
   for (n=1; n<10; n++)
   {
     ptr = str;
     while (*ptr != '\0')
     {
       while (strncmp(ptr, ptr + n, n) == 0)
         strcpy(ptr, ptr + n);
       ptr++;
     }
   }
 }

It could be optimized better, but, I choose to optimize the pseudo code to get the idea across. The problems with this code are:

• It’s inefficient because it uses strcpy (a src, dst pointer pair would be better)
• The ptr loop goes to the end of the string, we could abort earlier
• There’s a hard coded limit of 10 in there, this could be generalized
• This function overwrites the memory pointed to by str, whereas a copy may be better
• (EDIT) Change inner if to an inner while to ‘crunch’ repeated sequences.