/// <summary>
/// 在一个字符串找到第一个只出现一次的字符
/// </summary>
/// <returns></returns>
static string First(string str)
{
for (int i = 0; i < str.Length - 1; i++)
{
if (!str.Substring(i + 1, str.Length - i - 1).Contains(str.Substring(i, 1)) &&
!str.Substring(0, i).Contains(str.Substring(i, 1)))
{
return str.Substring(i, 1);
}
}
return string.Empty;
}

/// <summary>
/// 压缩字符串
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
static string YaSuo(string str)
{
string forY = str + "0";
string putValue = string.Empty;
int upCount = 0;
int count = 1;
for (int i = 1; i < forY.Length; i++)
{
if (forY.Substring(i, 1) != forY.Substring(upCount, 1))
{
putValue += forY.Substring(upCount, 1) + count;
upCount = i;
count =1;
}
else
{
count++;
}
}
return putValue;
}

/// <summary>
/// 翻转句子中单词顺序
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
static string Reverse(string str)
{
string[] array = str.Split(' ').ToArray();
Array.Reverse(array);
string value = string.Join(" ", array);
return value;
}