hi, i have C exam next week, so i started solving questions from previous years exams and run into this question, the answer i come up to is far far from having reasonable length, it's too complicated and long , but i can't come up anything shorter.

the question is: write a function that receives an array of letters , and a pointer to final result string that hasn't allocated yet, the function supposed to take the array of letters and count the appearance of every letter and make the final result string look like that:

received array of letters : "abbacdeefg"
result string: "a 2;b 2;c 1;d 1;e 2;f 1;g 1"
in the result it should be alphabetically printed

here is the code that i wrote, it just doesn't makes sense that this is the actual solution:

Code:
void sortarray(char str[],char * final)
{
    int i = 1,j, extra = 0;
    char * letters, *lerrptr;
    int * count, * cerrptr;
    int size = 0, flag = 0;

    // allocate memory for one array storing letter and one for storing it's appearance
    letters = (char *) malloc(sizeof(char) * 1);
    if(letters == NULL) exit(1);
    count = (int *) malloc(sizeof(int) * 1);
    if(count == NULL) exit(1);

    // fill the first letter to array
    letters[0] = str[0];
    count[0] = 1;
    size++;

    // scan the whole string
    while(str[i] != 0)
    {
        // initiate flag for new run
        flag = 0;

        for(j = 0 ; j < size ; j++)
        {
            // if the letter already appeared before just increment the count and raise the flag that no new allocating is necessary
            if(str[i] == letters[j]) 
            {
                count[j]++;
                flag = 1;
            }
        }    
        // if the flag of already appeared hasn't been raised make new allocation for new letter
        if(!flag)
        {
            flag = 0 ;
            size++;
            lerrptr = letters;
            letters = (char *) realloc(letters,sizeof(char) * size);
            if(letters == NULL)
            {
                free(lerrptr);
                free(count);
                exit(1);
            }
            cerrptr = count;
            count = (int *) realloc(count,sizeof(int) * size);
            if(letters == NULL)
            {
                free(cerrptr);
                free(letters);
                exit(1);
            }
            // insert new letter and 1 for the count
            letters[size-1] = str[i] ;
            count[size-1] = 1 ;
                
        }

        i++;
    }
        
    // bubble sort the letters 
    for(i = 0 ; i < size - 1; i++)
    {
        for(j = 0 ; j < size - 1 - i ; j++)
        {
            if(letters[j] < letters[j - 1])
            {
                letters[j] ^= letters[j+1];
                letters[j+1] ^= letters[j];
                letters[j] ^= letters[j+1];
                count[j] ^= count[j+1];
                count[j+1] ^= count[j];
                count[j] ^= count[j+1];
            }
        }
    }
    
    // check for more 9 appearances to reserve more letters for one more digit
    for(i = 0 ; i < size ; i++) if(count[i] > 9) extra++;

    // allocate the memory for the final array that is going to be printed
    final = (char *) malloc(sizeof(char) * (size * 4) + extra + 1);
    
    j = 0;
    for(i = 0 ; i < size ; i++)
    {
        // insert the letter
        final[i*4 + j] = letters[i];
        // insert space
        final[i*4 + 1 + j] = ' ';

        // if more then one digit used for the count of appearances
        if(count[i] > 9)
        {
            // first digit
            final[i*4 + 2 + j] = count[i]/10 + 48;
            j++;
            // second
            final[i*4 + 2 + j] = count[i]%10 + 48 ;
        }
        else final[i*4 + 2 + j] = count[i]  + 48;
        
        // print ; 
        final[i*4 + 3 + j] = ';';
    }

    // add terminating character
    final[i*4 + j] = 0;
    // print the result
    printf(" %s ", final);
}
can anyone help me come up with more reasonable solution?