Compress String

/* compress the string for example aabbbcccccdeff should become a2b3c5d1e1f2
 * if compress string length remain same as original string then return
 * original string */

using namespace std;

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

main() {

        string input;
        cout << " enter input string to be compressed: ";
        cin >> input;

        string::size_type len = input.size();

        string::size_type orig_len = len;

        string::size_type i = 0;

        int sameCharCount = 1;

        bool in_progress = false;

        char buf[10];

        while (i < len) {
   
                if (input[i] == input[i+1]) {
                        in_progress = true;
                        sameCharCount++;
                } else if (in_progress) {
                        in_progress = false;
                        sprintf(buf, "%d", sameCharCount);
                        input.replace(i-sameCharCount+2, sameCharCount-1, buf);

                        len = len - sameCharCount + 1 + strlen(buf);

                        i = i - sameCharCount + 1 + strlen(buf);

                        sameCharCount = 1;

                } else {

                        input.insert(i+1, "1");

                        i++;

                        len++;

                }

                i = i + 1;

        }

        if (input.size() < orig_len) {

                cout << "changed string: " << input << endl;

        } else {

                cout << "string was not compressed" << endl;

        }

}

$ ./a.out 

 enter input string to be compressed: aaabb

changed string: a3b2

$ ./a.out 

 enter input string to be compressed: ab

string was not compressed

$ ./a.out 

 enter input string to be compressed: acc

string was not compressed

$ ./a.out 

 enter input string to be compressed: b

string was not compressed

$ ./a.out 

 enter input string to be compressed: bc

string was not compressed

$ ./a.out 

 enter input string to be compressed: abc

string was not compressed

$ ./a.out 

 enter input string to be compressed: aaabbbbbbbbbbbbddddddddddd

changed string: a3b12d11