/// <summary>
/// 密碼強度
/// </summary>
private enum Strength
{
 Invalid = 0, //無效密碼
 Weak = 1, //低強度密碼
 Normal = 2, //中強度密碼
 Strong = 3 //高強度密碼
};
/// <summary>
/// 計算密碼強度
/// </summary>
/// <param name="password">密碼字符串</param>
/// <returns></returns>
private static Strength PasswordStrength(string password)
{
 //空字符串強度值為0
 if (password == "") return Strength.Invalid;
 //字符統(tǒng)計
 int iNum = 0, iLtt = 0, iSym = 0;
 foreach (char c in password)
 {
  if (c >= '0' && c <= '9') iNum++;
  else if (c >= 'a' && c <= 'z') iLtt++;
  else if (c >= 'A' && c <= 'Z') iLtt++;
  else iSym++;
 }
 if (iLtt == 0 && iSym == 0) return Strength.Weak; //純數(shù)字密碼
 if (iNum == 0 && iLtt == 0) return Strength.Weak; //純符號密碼
 if (iNum == 0 && iSym == 0) return Strength.Weak; //純字母密碼
 if (password.Length <= 6) return Strength.Weak; //長度不大于6的密碼
 if (iLtt == 0) return Strength.Normal; //數(shù)字和符號構(gòu)成的密碼
 if (iSym == 0) return Strength.Normal; //數(shù)字和字母構(gòu)成的密碼
 if (iNum == 0) return Strength.Normal; //字母和符號構(gòu)成的密碼
 if (password.Length <= 10) return Strength.Normal; //長度不大于10的密碼
 return Strength.Strong; //由數(shù)字、字母、符號構(gòu)成的密碼
}

static void Main(string[] args)
{
 string sPassword;
 while (true)
 {
  Console.WriteLine("請輸入一個密碼：");
  sPassword = Console.ReadLine();
  switch (PasswordStrength(sPassword))
  {
   case Strength.Invalid: Console.WriteLine("無效密碼\n"); break;
   case Strength.Weak: Console.WriteLine("低強度密碼\n"); break;
   case Strength.Normal: Console.WriteLine("中強度密碼\n"); break;
   case Strength.Strong: Console.WriteLine("高強度密碼\n"); break;
  }
 }
}