给定n个元素的排序数组，在线性时间内对n / 2个元素进行排序

I have a sorted array of n elements. Now I am given n/2 elements each of which belong to the sorted array. The n/2 elements are taken at random from the sorted array. How to sort these n/2 elements in linear time? I have a sorted array of n elements. Now I am g