667. Beautiful Arrangement II

Given two integers n and k, you need to construct a list which contains n different positive integers ranging from 1 to n and obeys the following requirement: 
Suppose this list is [a1, a2, a3, ... , an], then the list [|a1 - a2|, |a2 - a3|, |a3 - a4|, ... , |an-1 - an|] has exactly k distinct integers.

If there are multiple answers, print any of them.

Example 1:

Input: n = 3, k = 1
Output: [1, 2, 3]
Explanation: The [1, 2, 3] has three different positive integers ranging from 1 to 3, and the [1, 1] has exactly 1 distinct integer: 1.

Example 2:

Input: n = 3, k = 2
Output: [1, 3, 2]
Explanation: The [1, 3, 2] has three different positive integers ranging from 1 to 3, and the [2, 1] has exactly 2 distinct integers: 1 and 2.

Note:

1. The n and k are in the range 1 <= k < n <= 104.

题意：

1-n这些数，如何排列，使得 [|a1 - a2|, |a2 - a3|, |a3 - a4|, ... , |an-1 - an|]有k个不同的数。

思路：

很怪的一道题。首先如果k=n-1，那么就必然是1，n,2,n-1,3,n-2……这样最大的和最小的交替排列。如果k<n-1，那么就先排列，等到满足了k-1个，接下来的再全都是1即可。

代码：