algorithm - 选择排序顺序

Question

我的书说:

Suppose you have a group of N numbers and would like to determine the kth largest. This is known as the selection problem. Most students who have had a programming course or two would have no difficulty writing a program to solve this problem. There are quite a few “obvious” solutions. One way to solve this problem would be to read the N numbers into an array, sort the array in decreasing order.

它表示按降序对数组进行排序是有意义的。这有什么意义？如果我有一个 {1,9,3,7,4,6​​} 数组并且我想要最大的元素，我会按升序对它进行排序，这样 {1,3, 4,6,7,9} 然后返回最后一个元素。为什么书上会说降序？

Answer 1

因为你可能不想要最大的元素，书上说

would like to determine the kth largest

如果你按升序排序，你怎么知道第三大的数是多少而不首先找出数组有多大？

如果数组是递减的，这会更容易，因为第三大元素就是第三个元素。