C#统计字符串中字符出现的次数

方法1.自定义类

class CharNum
        {
            private char c;
            private int num;


            public char C
            {
                get { return c; }
            }

            public int Num
            {
                get { return num; }
                set { num = value; }
            }

            public CharNum(char ch)
            {
                this.c = ch;
                this.num = 1;
            }
        }
static void Main(string[] args)
        {
           /* */string s = "abbbcgg";
            IList<char> alist = new List<char>();
            for (int i = 0; i < s.Length; i++)
            {
                if (!alist.Contains(s[i]))
                    alist.Add(s[i]);
            }
            char[] c = (char[])alist.ToArray();
            int length = 0;
            CharNum[] data = new CharNum[c.Length];
            for (int j = 0; j < s.Length; j++)
            {
                CharNum cn = new CharNum(s[j]);
                bool plus = false;
                if (length == 0)
                {
                    data[length] = cn;
                    length++;
                }
                else
                {
                    for (int k = 0; k < length; k++)
                    {
                        if (data[k].C == cn.C)
                        {
                            data[k].Num++;
                            plus = true;
                            break;
                        }
                    }
                    if (!plus)
                    {
                        data[length] = cn;
                        length++;
                    }
                }
            }
            for (int i = 0; i < data.Length; i++)
            {
                Console.WriteLine("{0}:{1}",data[i].C.ToString(), data[i].Num.ToString());
            }
            Console.ReadKey();
}

方法2：键值集合 Dictionary<char, int>

                Dictionary<char, int> dic = new Dictionary<char, int>();
                String s = "aaabbs";
                char[] chardata = s.ToCharArray();

                foreach (char c in chardata)
                {
                    if (!dic.ContainsKey(c))
                    {
                        dic.Add(c, 1);
                    }
                    else
                    {
                        dic[c] = dic[c] + 1;
                    }
                }
                foreach (KeyValuePair<char, int> item in dic)
                {
                    Console.WriteLine("{0}出现{1}次", item.Key, item.Value);
                }
                Console.ReadLine();

方法3：哈希表

                Hashtable ht = new Hashtable();
                string sr = "aaabbcddddd";
                char[] cr = sr.ToCharArray();
                foreach (char ch in cr)
                {
                    if (ht.ContainsKey(ch))
                    {
                        int i = (int)ht[ch];
                        ht.Remove(ch);
                        ht.Add(ch, ++i);
                    }
                    else
                        ht.Add(ch, 1);
                }
                foreach (DictionaryEntry dicEntry in ht)
                {
                    Console.WriteLine("{0}出现{1}次", dicEntry.Key, dicEntry.Value);
                }
                ArrayList alist = new ArrayList(ht.Values);
                alist.Sort();
                object o = (object)alist[alist.Count - 1];
                foreach (DictionaryEntry dicEntry in ht)
                {
                    if (dicEntry.Value == o)
                    {
                        string str = dicEntry.Key.ToString();
                        Console.WriteLine("出现次数最多的字符:{0}，共{1}次", str, o.ToString());
                        break;
                    }
                }
                Console.ReadLine();

方法4：LINQ

            string s = "aaabccccef";
            char[] c = s.ToCharArray();
            var cc = c.GroupBy(e => e).OrderByDescending(e => e.Count()).ToList();
            for (int i = 0; i < cc.Count; i++)
            {
                Console.WriteLine("{0}\t{1}", cc[i].Key.ToString(), cc[i].Count().ToString());
            }
            var ccc = c.GroupBy(e => e).OrderByDescending(e => e.Count()).First().ToList();
    
            Console.WriteLine("{0}出现{1}次！", ccc[0].ToString(), ccc.Count().ToString());
            Console.ReadKey();