using System;
using System.Linq;
using System.Collections.Generic;
namespace Yoba{
public class Test
{
public static void Main()
{
var source = new int[] {1, 2, 3, 4, 5, 6, 7};
Action<int[]> output = (t) => Console.WriteLine(t.Aggregate(string.Empty, (s, s1)=>string.Format("{0}, {1}", s, s1)).Trim(new char[]{',',' '}));
output(source);
source = Enumerable.Range(0, source.Length).Select(x => source[Math.Min(x + 1 - x % 2 * 2, source.Length - 1)]).ToArray();
output(source);
}
}
}
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1, 2, 3, 4, 5, 6, 7
2, 1, 4, 3, 6, 5, 7