设a[0:n-1]是有n个元素的数组，k(0≤k≤n-1)是一个非负整数。试设计一个算法将子数组a[0:k-1]与a[k:n-1]换位。要求算法在最坏的情况下耗时0（n),且只用到0（1）的辅助空间。-Let A [0: n-1] is an array of n elements, k (0 ≤ k ≤ n-1) is a non-negative integer. The trial design of an algorithm of the sub-array A [0: k-1] and