剔除字符串中重复的字符

 

public string distinctChar(string source)
    {
        char[] srcArr = source.ToCharArray();
        //标识数组 2048 = 65535/32 + 1
        //每一位(Bit)都标识一个字符，1表示字符已经出现过，0表示字符尚未出现，初始全为0
        int[] fArr = new int[2048];
        int shift;
        string dStr = "";
        for (int i = srcArr.Length - 1; i >= 0; i--)
        {
            shift = 1;
            shift <<= srcArr[i] % 32;
            if (0 == (shift & fArr[srcArr[i] >> 5]))
            {
                dStr+=srcArr[i];
                fArr[srcArr[i] >> 5] += shift;
            }
        }
        return dStr;
    }