题解 | #计算某字符出现次数#

using System;
using System.Collections.Generic;

namespace Huawei
{
    class Solution
    {
        static void Main(string[] args)
        {
            string inputString=Console.ReadLine().ToLower();
            string letter=Console.ReadLine().ToLower();//以上输入全部转成小写
            
            int num=0;
            int L=0, R=inputString.Length-1;
            
            while(L<R)//双指针并没有快多少
            {
                if(inputString[L++]==letter[0]) num++;
                if(inputString[R--]==letter[0]) num++;
            }
            
            
            Console.WriteLine(num);
        }
    }
}