Question

Somewhere in my program I get these outputs:

ee

or:

thht

Basically I want to remove the duplicates to obtain e or th. I got this code:

j = 0;
for (i = 1; i < strlen(erros); i++)
{
    if (erros[j] != erros[i])
    {
        erros[j+1] = erros[i];
        j++;
    }
}

This code gives me e and tht. If in the first case its OK, in the second its not. I believe it is due because I don’t have a sorted array.

Is there a way, without sorting the array and using the above code, to obtain the desired output?

Answer 1

You can create an array of flags, one for each possible character value. The first time you encounter a particular character value, set the flag. The next time you encounter that value, the flag will be set, indicating that you can remove that character.

Along the lines of (untested):

int flags[1 << CHAR_BIT];
memset(flags, 0, sizeof(flags));
j = 0;
for (i = 0; i < strlen(erros); i++)
{
    erros[j] = erros[i];  // Always copy, it's simpler
    if (!flags[erros[i]])
    {
        j++;
    }
    flags[erros[i]] = 1;  // Always set the flag, it's simpler
}
erros[j] = '\0';

Note: You are forgetting to set the NULL terminator in your string.