C# 寻找第一个不重复的字符

        static char FirstUniqueChar(string str)
        {
            if (str== null|| str.Length == 0)
            {
                throw new Exception("Input can't be empty");
            }
            char[] chrArr = str.ToCharArray();
            Hashtable ht = new Hashtable();
            for (int i = 0; i < str.Length; i++)
            {
                if (ht.Contains(str[i])==false)
                {
                    ht.Add(str[i], 1);
                }
                else
                {
                    ht[str[i]] = 2;
                }
            }
            for (int i = 0; i < str.Length; i++)
            {
                if (ht[str[i]].ToString()=="1")
                {
                    return str[i];
                }
            }
            throw new Exception("No unique char.");
        }

 网上查找了下，找到了LINQ的实现，太惊艳了，30行变成3行。

        static char FirstUChar(string str)
        {
            var filter = str.ToCharArray().GroupBy(s => s).Where(g => g.Count() == 1).Select(g => g.Key);
            var result = string.Join("", filter.ToArray());
            return result[0];
        }