6. 依資料出現頻率來排序

while (true)
{
var s=    Console.ReadLine();
    if (s.Length == 0) return;
    Dictionary<Char, int> map = new Dictionary<char, int>();
    foreach (var item in s)
    {
        map[item] = (map.GetValueOrDefault(item,0)) + 1;
    }

    var all= map.ToList().OrderByDescending(e => e.Value).ToList();
    for (global::System.Int32 i = 0; i < all.Count; i++)
    {
        var v = all[i];
        Console.Write($"\"{v.Key}\" = {v.Value}");
        if (i != all.Count - 1) Console.Write(" ; ");
    }
}