HJ59 找出字符串中第一个只出现一次的字符

HJ59 找出字符串中第一个只出现一次的字符

void FindOnly(string& s)
{
    int flag = 0, a[128] = { 0 };
    int len = s.size(); 
    char c;
    for (int i = 0; i < len; i++)
        a[s[i]] += 1; 
    for (int i = 0; i < len; i++)
    {
        if (a[s[i]] == 1)
        {
            flag = 1;
            c = s[i];
            break; 
        }
    }
     if (flag)
        cout << c << endl; 
    else
        cout << -1 << endl;
}
int main()
{
    string s;
    while (getline(cin, s))
        FindOnly(s);
    return 0;
}