剑指offer---第一个只出现一次的字符

class Solution 
{
public:
    int FirstNotRepeatingChar(string str) 
    {
        
        int str_size = str.size();
        

        for (int i = 0; i < str_size; ++i)
        {
            for (int j = 0; j < str_size; ++j)
            {
                if (i == j)
                {
                    continue;
                }
                else if (str[i] == str[j])
                {
                    break;
                }
                else if (j == (str_size - 1) && str[j] != str[i])
                {
                    return i;
                }

            }
            
        }
        return -1;

        

    }
};

没用哈希