c# 选择排序

class Program
    {
        static void Main(string[] args)
        {
            int[] arr = new int[] { 6, 9, 13, 2, 4, 64 };
            int[] newArr = SelectionSort(arr);
            Console.Read();
        }
        public static int[] SelectionSort(int[] a)
        {
            int item; //中间临时变量，用于交换元素位置
            for (int i = 0; i < a.Length; i++)
            {
                int minIndex = i; //记录最小元素的下标
                for (int j = i+1; j < a.Length; j++)
                {
                    if (a[minIndex]>a[j])
                    {
                        minIndex = j;
                    }
                }
                if (a[minIndex]!=a[i])
                {
                    item = a[i];
                    a[i] = a[minIndex];
                    a[minIndex] = item;
                }
                StringBuilder sb = new StringBuilder();
                sb.Append($"第{i+1}次排序后：");
                foreach (var num in a)
                {
                    sb.Append($"{num},");
                }
                Console.WriteLine(sb.ToString());
            }
            return a;
        }
    }