Reverse the element of array between the startIndex and endIndex. - CSharp System

CSharp examples for System:Array Index

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Description

Reverse the element of array between the startIndex and endIndex.

Demo Code


using System.Threading.Tasks;
using System.Text;
using System.Linq;
using System.Diagnostics.Contracts;
using System.Collections.Generic;
using System;//from  w w w. j a  va  2  s  .c  o  m

public class Main{
        /// <summary>
        /// Reverse the element of array between the startIndex and endIndex.
        /// </summary>
        /// <typeparam name="TElement"></typeparam>
        /// <param name="ary"></param>
        /// <param name="startIndex">zero-based start index</param>
        /// <param name="length">length to reverse</param>
        /// <exception cref="ArgumentNullException">array is null</exception>
        /// <exception cref="IndexOutOfRangeException"> startIndex or length less than zero, 
        /// or startIndex plus length indicates a position out of range .</exception>
        public static void ReverseArray<TElement>(this TElement[] ary, int startIndex, int length)
        {
            if (ary == null)
                throw new ArgumentNullException(nameof(ary));
            if (startIndex < 0)
                throw new IndexOutOfRangeException("startIndex less than zero");
            if (length < 0)
                throw new IndexOutOfRangeException("length less than zero");
            if (startIndex + length > ary.Length)
                throw new IndexOutOfRangeException("position out of range.");

            InternalReverseArray(ary, startIndex, length);
        }
        /// <summary>
        /// Reverse the element of array
        /// </summary>
        /// <typeparam name="TElement"></typeparam>
        /// <param name="ary"></param>
        /// <exception cref="ArgumentNullException">array is null</exception>
        public static void ReverseArray<TElement>(this TElement[] ary)
        {
            if (ary == null)
                throw new ArgumentNullException(nameof(ary));

            InternalReverseArray(ary, 0, ary.Length);
        }
        internal static void InternalReverseArray<TElement>(TElement[] ary, int startIndex, int length)
        {
            Contract.Requires(ary != null);
            Contract.Requires(length >= 0);
            Contract.Requires(startIndex >= 0);
            Contract.Requires(startIndex + length <= ary.Length);

            int endIndex = startIndex + length - 1;
            while (startIndex < endIndex)
            {
                TElement tmp = ary[startIndex];
                ary[startIndex] = ary[endIndex];
                ary[endIndex] = tmp;

                startIndex++;
                endIndex--;
            }
        }
}

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