ListHelper.cs :  » Game » SokoSolve-Sokoban » SokoSolve » Common » C# / CSharp Open Source

using System;
using System.Collections.Generic;
using System.Text;

namespace SokoSolve.Common{
  public static class ListHelper
  {
    static private Random random = new Random();

        /// <summary>
        /// Helper to resize an array
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="Source"></param>
        /// <param name="NewItem"></param>
        /// <returns></returns>
        public static T[] AddToArray<T>(T[] Source, T NewItem)
        {
            if (Source == null || Source.Length == 0)
            {
                T[] newresult = new T[1];
                newresult[0] = NewItem;
                return newresult;
            }

            T[] result = new T[Source.Length+1];
            Source.CopyTo(result, 0);
            result[result.Length - 1] = NewItem;
            return result;
        }


    /// <summary>
    /// Select a single item randomly from a list
    /// </summary>
    public static T RandomSelection<T>(IList<T> list)
    {
      return list[random.Next(0, list.Count)];
    }

    /// <summary>
    /// Return the first item from a list (null if not present)
    /// </summary>
    public static T First<T>(IList<T> list)
    {
      if (list == null || list.Count == 0) return default(T);
      return list[0];
    }

    /// <summary>
    /// Return the last item from a list (null if not present)
    /// </summary>
    public static T Last<T>(IList<T> list)
    {
      if (list == null || list.Count == 0) return default(T);
      return list[list.Count - 1];
    }

    /// <summary>
    /// Select a number of items from a list, randomly, without duplicates
    /// </summary>
    public static List<T> RandomSubSet<T>(IList<T> source, int count)
    {
      List<T> current = new List<T>(source);
      List<T> results = new List<T>();

      for (int cc = 0; cc < count; cc++)
      {
        if (current.Count == 0) return results;

        T selection = current[random.Next(0, current.Count)];
        current.Remove(selection);
        results.Add(selection);
      }
      return results;
    }

    /// <summary>
    /// See if a list has duplicates (order will be sorted)
    /// </summary>
    public static bool HasDuplicates<T>(List<T> inputList)
    {
      // No duplicates
      if (inputList == null || inputList.Count == 1) return false;

      // Sort, then see if any two object in sequence are equal.
      inputList.Sort();
      for (int cc = 0; cc < inputList.Count - 1; cc++)
      {
        if (inputList[cc].Equals(inputList[cc + 1]))
        {
          // Two object in sequnce are equal -> duplicates exist
          return true;
        }
      }
      return false;
    }

    /// <summary>
    /// Count the number of items which return true to a predicate.
    /// </summary>
    public static int Count<T>(IList<T> inputList, Predicate<T> predicate)
    {
      if (inputList == null) return 0;

      int count = 0;
      foreach (T item in inputList)
      {
        if (predicate(item)) count++;
      }
      return count;
    }
  }
}