Binärsuche innerhalb einer Liste

namespace System.Collections
{
	/// <summary>
	/// Performs a binary search within any implementation
	/// of <see cref="System.Collections.IList"/>.
	/// </summary>
	public static class IListBinarySearchExtension
	{
		/// <summary>
		/// Searches for an <paramref name="item"/> within the specified <paramref name="list"/>
		/// using the specified <paramref name="comparer"/>.
		/// </summary>
		/// <typeparam name="T">The type of the list.</typeparam>
		/// <param name="list">The list to search in.</param>
		/// <param name="comparer">The function used to compare the list's elements.</param>
		/// <param name="item">The result of the search.</param>
		/// <returns>Returns <b>true</b> on success; <b>false</b> on failure.</returns>
		public static bool BinarySearch<T>(this IList list, Func<T, int> comparer, out T item)
		{
			if (list == null)
				throw new ArgumentNullException("list");
			if (comparer == null)
				throw new ArgumentNullException("comparer");

			return BinarySearch(list, comparer, 0, list.Count - 1, out item);
		}

		/// <summary>
		/// Searches for an <paramref name="item"/> within the specified range of the specified
		/// <paramref name="list"/> using the specified <paramref name="comparer"/>.
		/// </summary>
		/// <typeparam name="T">The type of the list.</typeparam>
		/// <param name="list">The list to search in.</param>
		/// <param name="comparer">The function used to compare the list's elements.</param>
		/// <param name="item">The result of the search.</param>
		/// <param name="min">The lower bound of the search.</param>
		/// <param name="max">The upper bound of the search.</param>
		/// <returns>Returns <b>true</b> on success; <b>false</b> on failure.</returns>
		public static bool BinarySearch<T>(this IList list, Func<T, int> comparer, int min, int max, out T item)
		{
			if (list == null)
				throw new ArgumentNullException("list");
			if (comparer == null)
				throw new ArgumentNullException("comparer");
			if (min < 0 || min >= list.Count)
				throw new ArgumentOutOfRangeException("min");
			if (max < 0 || max >= list.Count)
				throw new ArgumentOutOfRangeException("max");

			while (min <= max)
			{
				int middle = min + ((max - min) / 2);
				int compared = comparer((T)list[middle]);

				if (compared < 0)
				{
					min = middle + 1;
				}
				else if (compared > 0)
				{
					max = middle - 1;
				}
				else
				{
					item = (T)list[middle];
					return true;
				}
			}

			item = default(T);
			return false;
		}
	}
}

namespace System.Collections
{
	/// <summary>
	/// Performs a binary search within any implementation
	/// of <see cref="System.Collections.IList"/>.
	/// </summary>
	public static class IListBinarySearchExtension
	{
		/// <summary>
		/// Searches for an <paramref name="item"/> within the specified <paramref name="list"/>
		/// using the specified <paramref name="comparer"/>.
		/// </summary>
		/// <typeparam name="T">The type of the list.</typeparam>
		/// <param name="list">The list to search in.</param>
		/// <param name="comparer">The function used to compare the list's elements.</param>
		/// <param name="item">The result of the search.</param>
		/// <returns>Returns <b>true</b> on success; <b>false</b> on failure.</returns>
		public static bool BinarySearch<T>(this IList list, Func<T, int> comparer, out T item)
		{
			if (list == null)
				throw new ArgumentNullException("list");
			if (comparer == null)
				throw new ArgumentNullException("comparer");

			return BinarySearch(list, comparer, 0, list.Count - 1, out item);
		}

		/// <summary>
		/// Searches for an <paramref name="item"/> within the specified range of the specified
		/// <paramref name="list"/> using the specified <paramref name="comparer"/>.
		/// </summary>
		/// <typeparam name="T">The type of the list.</typeparam>
		/// <param name="list">The list to search in.</param>
		/// <param name="comparer">The function used to compare the list's elements.</param>
		/// <param name="item">The result of the search.</param>
		/// <param name="min">The lower bound of the search.</param>
		/// <param name="max">The upper bound of the search.</param>
		/// <returns>Returns <b>true</b> on success; <b>false</b> on failure.</returns>
		public static bool BinarySearch<T>(this IList list, Func<T, int> comparer, int min, int max, out T item)
		{
			if (list == null)
				throw new ArgumentNullException("list");
			if (comparer == null)
				throw new ArgumentNullException("comparer");
			if (min < 0 || min >= list.Count)
				throw new ArgumentOutOfRangeException("min");
			if (max < 0 || max >= list.Count)
				throw new ArgumentOutOfRangeException("max");

			while (min <= max)
			{
				int middle = min + ((max - min) / 2);
				int compared = comparer((T)list[middle]);

				if (compared < 0)
				{
					min = middle + 1;
				}
				else if (compared > 0)
				{
					max = middle - 1;
				}
				else
				{
					item = (T)list[middle];
					return true;
				}
			}

			item = default(T);
			return false;
		}
	}
}

Alte URL: /snippet/binaersuche-innerhalb-einer-liste/902