如何在C#中对数组列表的元素进行排序

Question

I have an ArrayList that contains,

[0] = "1"
[1] = "10"
[2] = "2"
[3] = "15"
[4] = "17"
[5] = "5"
[6] = "6"
[7] = "27"
[8] = "8"
[9] = "9"

Now i need to sort the array list such that it becomes,

[0] = "1"
[1] = "2"
[2] = "5"
[3] = "6"
[4] = "8"
[5] = "9"
[6] = "10"
[7] = "15"
[8] = "17"
[9] = "27"

At last i will be getting the values from ArrayList and using them as 'int' values. How can i do this? Or shall i convert them to int at first and then sort them.?

Answer 1

If you can be sure the list contains only strings that can be transformed to integers, then with the IEnumerable<T>.OrderBy extension method, try this:

var sortedList = list.OrderBy(item => int.Parse(item));

If you're using an ArrayList instead of a List<string> (boo!), you'll need to Cast first:

var sortedList = list.Cast<string>().OrderBy(item => int.Parse(item));

You can also define your own comparer as JaredPar noted, but IMO that's a lot of work for something that's already implemented. However, it's more efficient.

Answer 2

There are numerous sort methods in the framework including ArrayList.Sort. The problem is that they are all going to sort alphabetically and not numerically. You'll need to write a custom sorter that understands numeric sorts.

Try the following (some argument checking left out for brevity)

public class NumericComparer : IComparer {
  public int Compare(object x, object y) {
    string left = (string)x; 
    string right = (string)y;
    int max = Math.Min(left.Length, right.Length);
    for ( int i = 0; i < max; i++ ) {
      if ( left[i] != right[i] ) { 
        return left[i] - right[i];
      }
    }
    return left.Length - right.Length;
  }
}

list.Sort(new NumericComparer());

Answer 3

Implement custom comparer and pass it to ArrayList.Sort()

Complete Code:

using System;
using System.Collections;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            ArrayList a = new ArrayList();
            a.Add("1");
            a.Add("13");
            a.Add("3");
            a.Add("25");
            a.Add("2");
            a.Add("12");
            a.Sort(new CustomComparer());

            foreach (String s in a)
                Console.WriteLine(s);

            Console.Read();
        }


    }

    public class CustomComparer : IComparer
    {
        Comparer _comparer = new Comparer(System.Globalization.CultureInfo.CurrentCulture);

        public int Compare(object x, object y)
        {
            // Convert string comparisons to int
            return _comparer.Compare(Convert.ToInt32(x), Convert.ToInt32(y));
        }
    }
}

Output:

1 2 3 12 13 25

Answer 4

Maybe you could store the values in a strongly typed list like List instead, and the, if necessary, convert them to string, when cosuming them. Like this:

        List<int> intList = new List<int>(new int[] {3, 2, 1});

        intList.Sort();

        foreach (int theInt in intList)
        {
            System.Diagnostics.Debug.WriteLine(theInt.ToString());
        }

Answer 5

You'll be better of creating another array with Int values and then sorting it with ArrayList.Sort() . You could call ArrayList.Sort() and pass it a delegate that will compare those strings as numbers but it will be slower. How much slower depends on size of your array and I personally think for sizes less then 100 it doesn't really matter.

Answer 6

Arraylist Sort(CaseSensitive) in Ascending Order Helpful for someone

class ArrayCaseSensitive:IComparer
    {
        int IComparer.Compare(object x, object y)
        {
            return (new CaseInsensitiveComparer().Compare(x,y));
        }

    public static void Main(string[] args)
    {
            IComparer sc = new ArrayCaseSensitive();
           
        ArrayList arr = new ArrayList();
        arr.Add("AB");
        arr.Add("bc");
        arr.Add("1");
        arr.Sort(sc);
        foreach(var strs in arr)
        {
            Console.WriteLine(strs);
        }
        
    }

}

Answer 7

If the values are all ints then why not store them as ints? That would make sorting easier and faster.

In what other ways are the values used? If they're only used as strings and only sorted once then it's probably sensible to leave them as they are - as strings.

On the other hand, if they're used in maths ops then it's best to store them as ints.

Answer 8

 List<int> liDllCnt = new List<int>();
 for (int temp = 0; temp < alFileName.Count; temp++)
     liDllCnt.Add(Int32.Parse(alFileName[temp].ToString()));
 liDllCnt.Sort();

alFileName is the name of the arraylist that i used.

Answer 9

This is the safest way

aryList is your ArrayList instance

                object[] list = aryList.ToArray();
                Array.Sort<object>
                    (
                        list,
                        delegate(object x, object y)
                        {
                            int a = 0, b = 0;
                            if (x == y) return 0;
                            if (x == null || y == null)
                                return x == null ? -1 : 1;
                            int.TryParse(x.ToString(), out a);
                            int.TryParse(y.ToString(), out b);
                            return a.CompareTo(b);
                        }
                    );

result saved into "list" object array

Answer 10

If you can get the ArrayList items into a strongly typed container such as List<String> or String[] then Linq makes it easy to do the rest. The following implementation parses the string values only once and creates an anonymous type for each with the original string and its integer value.

public void Test_SortArrayList()
{
    ArrayList items = new ArrayList(new []{"1", "10", "2", "15", "17", "5", "6", "27", "8", "9"});
    string[] strings = (string[])items.ToArray(typeof(string));
    List<string> result = strings
        .Select(x => new
            {
                Original = x,
                Value = Int32.Parse(x)
            })
        .OrderBy(x => x.Value)
        .Select(x => x.Original)
        .ToList();
    result.ForEach(Console.WriteLine);
}