在List中查找项目是否在C＃中多次出现

Question

In addition to the question: Get List<> element position in c# using LINQ

First of all, let me explaing why I do what I do :)

I'm trying to encrypt a string into a one-line code which holds how many times a letter is used in the string and also with its positions. By this method, I'll be able to decrypt the code and get(reproduce) the full text again. Let's say myString is "How are you today". I'll encrypt it like o3[1,9,13]," "3[3,7,11],a2[4,15],y2[9,17],H1[0],w1[2],r1[5],e1[6],u1[10],t1[12],d1[14],?[18]

I know it looks odd but think about working on bigger strings like e-books. This could handle all the text in one or two lines.

The encryption is not about the security, it's just about holding big datas in smaller spaces.

In my code, I can convert the string into list, count how many times a letter is used but I can't define the positions of the letters when they occur more than once.

private void btnKoda_Click(object sender, EventArgs e)
    {
        var yazi = txtYazi.Text;
        List<char> liste = yazi.ToList();
        List<string> tut = new List<string>();

        foreach (char harf in liste)
        {
            for (int i = 0; i < liste.Count; i++)
            {
                char ekle = liste[i];
                tut.Add(ekle.ToString());
            }

            foreach (var karakter in tut)
            {
                txtKod.Text += karakter;
            }

            // holds statics
            var istatistik =
                from c in tut
                group c by c into g
                select new { g.Key, say = g.Count() };
            var enCok =
                from giris in istatistik
                orderby giris.say descending
                select giris;
            foreach (var giris in enCok)
            {
                txtHarfler.Text += string.Format("{0}: {1}\r\n", giris.Key, giris.say);
            }

            break;

        }

Answer 1

Not sure what's going on in your code, but here's how I would do it:

    private void button1_Click(object sender, EventArgs e)
    {
        Dictionary<Char, Encoding> dct = new Dictionary<char, Encoding>();

        string data = "How are you today";
        for(int i = 0; i < data.Length; i++)
        {
            Char C = data[i];
            if (!dct.ContainsKey(C))
            {
                dct.Add(C, new Encoding(C));
            }
            dct[C].AddOccurence(i);
        }

        StringBuilder SB = new StringBuilder();
        foreach(Encoding enc in dct.Values)
        {
            if (SB.Length == 0)
            {
                SB.Append(enc.ToString());
            }
            else
            {
                SB.Append("," + enc.ToString());
            }
        }

        Console.WriteLine(SB.ToString());
    }

Here's the Encoding class:

    public class Encoding
    {

        private Char _C;
        private List<int> _Positions;

        private Encoding() {}

        public Encoding(Char C)
        {
            this._C = C;
            this._Positions = new List<int>();
        }

        public Char Character
        {
            get
            {
                return _C;
            }
        }

        public int Count
        {
            get
            {
                return _Positions.Count;
            }
        }

        public int[] Occurences
        {
            get
            {
                return _Positions.ToArray();
            }
        }

        public override string ToString()
        {
            string[] values = Array.ConvertAll(this.Occurences.ToArray(), x => x.ToString());
            return this.Character.ToString() + this.Count.ToString() + "[" + String.Join(",", values) + "]";
        }

        public void AddOccurence(int position)
        {
            this._Positions.Add(position);
        }

    }

Original String:

How are you today

Output:

H1[0],o3[1,9,13],w1[2], 3[3,7,11],a2[4,15],r1[5],e1[6],y2[8,16],u1[10],t1[12],d1[14]