输出和输入失配气泡排序算法

Question

为了学习冒泡排序算法，我输入了以下1、9、5、4、2

    var arr = new int[] { 1, 9, 5, 4, 2 };

    var rightVal = 0;
    var leftVal = 0;
    var leftIndex = 0;


    for (int i = arr.Length - 1; i >= 0; i--)
    {

        var val = arr[i];
        for (int j = i; j >= 0; j--)
        {
            if (j > 0)
            {
                leftIndex = j - 1;
            }
            else if (j == 0)
            {
                leftIndex = 0;
            }

            leftVal = arr[leftIndex];


            if (val < leftVal)
            {

                arr[j] = leftVal;
                arr[j - 1] = val;
            }
        }
    }
}

但是这产生了1,2,5,9,4的输出，我做错了什么？谢谢

Answer 1

var arr = new int[] { 1, 9, 5, 4, 2 };

var leftVal = 0;

for (int i = arr.Length - 1; i >= 1; i--)
{
    var val = arr[i];
    for (int j = i-1; j >= 0; j--)
    {
        leftVal = arr[j];
        if (val < leftVal)
        {
            arr[i] = leftVal;
            arr[j] = val;
            val = leftVal;
        }
    }
}