假设随便输入字符串 adfdfkeaaaldcleidlfadtuduu 判断出 有多少个a 多少个d 等等

Code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Collections;
using System.IO;
namespace FindNumber
{
    class Program
    {
        //方法1
        static void Method_1(string s)
        {
            Console.WriteLine("Method_1");
            //定义一个字典变量
            Dictionary<char, int> dict = new Dictionary<char, int>();
            for (int i = 0; i < s.Length; i++)
            {
                //检查该字典中是否有该键值
                if (dict.ContainsKey(s[i]))
                {
                    dict[s[i]] = dict[s[i]] + 1;
                }
                else
                {
                    dict.Add(s[i],1);
                }
            }
            //printf
            foreach(KeyValuePair<Char, int> dd in dict)
            {
                Console.WriteLine("{0}:{1}",dd.Key,dd.Value);
            }
        }
        //方法2
        static void Method_2(string s)
        {
            Console.WriteLine("Method_2");
            //正则表达式变量

            Regex reg = new Regex(@"a");
            //要匹配的字符串
            MatchCollection mac = reg.Matches(s);
            int a = 0;
            foreach (Match m in mac)
            {
                a = Regex.Matches(s,m.Value).Count;
            }
            Console.WriteLine(a);

        }
        //方法3
        static void Method_3(string s)
        {
            Console.WriteLine("Method_3");
            Regex reg = new Regex(@"a",RegexOptions.Singleline);
            Console.WriteLine(reg.Matches(s).Count);
        }
        //方法4
        static void MEthod_4(string s)
        {
            Console.WriteLine("Method_4");
            char[] a = s.ToCharArray();
            Hashtable table = new Hashtable();
            for (int i = 0; i < a.Length; i++)
            {
                if (s.Substring(0, i).IndexOf(a[i]) == -1)//这个什么用啊？？？a[i]第一次出现的位置,避免重复计算.ok!!
                {
                    int count = 0;
                    foreach (char x in a)
                    {
                        if (x == a[i])
                        {
                            count++;
                        }
                    } table.Add(a[i], count);
                }
            }
            //输出
            foreach (object o in table.Keys)
            {
                char b = (char)o;
                Console.WriteLine("{0}--{1}",b,table[b].ToString());
            }
        }
        //方法5
        static void Method_5(string s)
        {
            Console.WriteLine("Method_5");
            int cnt = 0;
            //
            while ((cnt = s.Length) != 0)
            {
                string sub = s.Substring(0,1);
                s = s.Replace(sub,"");
                cnt -= s.Length;
                Console.WriteLine(sub+"--"+cnt.ToString());
            }
        }
        //方法6
        static void Method_6(string s)
        {
            Console.WriteLine("Method_6");
          var queryStr = from item in s
                         group item by item;
          string str = "";
          foreach (var ss in queryStr)
          {
              str += ss.Key + "--" + ss.Count()+"\n";
          }
            //输出
          Console.WriteLine(str);
        }
        //方法7
        static void Method_7(string s)
        {
           
            Console.WriteLine("Method_7");
            var query = from c in s.ToCharArray()
                        group c by c into dic
                        select dic;
            foreach (var iter in query)
            {
                Console.WriteLine(iter.Key+"--"+iter.Count());
            }

        }
        //方法8
        static void Method_8(string s)
        {
            Console.WriteLine("MEthod_8");
            int cnt = 0;
            while ((cnt = s.Length) != 0)
            {
                string sub = s.Substring(0,1);
                s = s.Replace(sub,"");
                cnt -= s.Length;
                Console.WriteLine(sub+"--"+cnt.ToString());

            }
        }
        //方法9
        static void Method_9(string s)
        {
            Console.WriteLine("Method_9");
            string a = "";
            int count = 0;
            int strLength = s.Length;
            while (strLength > 0)
            {
                a = s.Substring(0,1);
                s = s.Replace(a,"");
                count = strLength - s.Length;
                strLength = s.Length;
                Console.WriteLine(a+"--"+count);
            }

        }
        //方法10
        static void Method_10(string s)
        {
            Console.WriteLine("Method_10");
            (from c in "adfdfkeaaaldcleidlfadtuduu"
             group c by c into g
             select string.Format("'{0}': {1}", g.Key, g.Count())).ToList().ForEach(Console.WriteLine);
        }
        static void Main(string[] args)
        {
            Console.WriteLine("Enter the string :");
            string s = Console.ReadLine();
            Method_1(s);
            Method_2(s);
            Method_3(s);
            MEthod_4(s);
            Method_5(s);
            Method_6(s);
            Method_7(s);
            Method_8(s);
            Method_9(s);
            Method_10(s);
            Console.ReadKey();
        }
    }
}

转载于:https://www.cnblogs.com/binlyzhuo/archive/2009/06/06/1497675.html