How to find the first non-repeated character in a string of n length?

Question

For example: It returns ‘b’ when the input is “abaccdeff”.

Answer 1

If you have plenty of memory then try the following code in C (may not be the best way)

unsigned char find_first_non_repeat(unsigned char *string)
{
    int chars[256];
    int i=0;
    memset(chars, 0, sizeof(chars));

    while (string[i++])
        chars[string[i]]++;

    i = 0;
    while (string[i++])
        if (chars[string[i]] == 1) return string[i];

    return 0xFF; // 0xff means no non-repeat character
}