帮助售书员

描述：

售书员将所有书籍通过从A-Z的26个大写字母来分类，每本书的编码由三个以上的大写字母组成，编码的首字母为书籍类别。在售书员的存货单里，每个编码后边都跟着一个空格和一个正整数，代表该书的库存数量。请帮助售书员统计某类别书籍的数量。

例如：

存货单数组：L = {“ABART 20”, “CDXEF 50”, “BKWRK 25”, “BTSQZ 89”, “DRTYM 60”}.

类别数组： M = {“A”, “B”, “C”, “W”}

返回字符串： (A : 20) - (B : 114) - (C : 50) - (W : 0)

表示A类别书籍的数量为20，B类别为114,C类别为50，W类别为0。

注意：若存货单或类别的数组为空，则返回空字符串。

MyCode:

using System;

public class StockList {

    public static string stockSummary(String[] lstOfArt, String[] lstOf1stLetter)
        {
            string retStr = "";
            if(lstOfArt.Length == 0 || lstOf1stLetter.Length == 0) return retStr;
            for (int i = 0; i < lstOf1stLetter.Length; i++)
            {
                int qty = 0;
                foreach (var s in lstOfArt)
                {
                    if (s[0].ToString() == lstOf1stLetter[i])
                    {
                        qty += Convert.ToInt32(s.Substring(s.IndexOf(' ')));
                    }
                }
                retStr += String.Format("({0} : {1}) - ", lstOf1stLetter[i], qty);
            }
            return retStr.Substring(0,retStr.Length - 3);
        }
}

CodeWars:

using System;
using System.Linq;

public class StockList {

    public static string stockSummary(String[] lstOfArt, String[] lstOf1stLetter) {

    if(lstOfArt.Length == 0 || lstOf1stLetter.Length == 0) return String.Empty;
    //Manageble list for calculations
    var maBookList = lstOfArt.Select(l => new Books(l));

    var result = lstOf1stLetter.Select( l => innerResult(l, maBookList.Where(m => m.Initial == l[0]).Sum(m => m.Quantity)));

    return String.Join(" - ", result);
    }
    //Internal string format helper
    private static string innerResult(string initial, int number)
    {
     return String.Format("({0} : {1})", initial, number);
    }   
}

public class Books {
 public char Initial {get; set;}
 public int Quantity {get; set;}
 public Books(string books)
 {
   Initial = books[0];
   Quantity = Convert.ToInt32(books.Split(' ')[1]);
 } 
}