Given an array A of integers, for each integer A[i] we need to
choose either x = -K or x = K, and add
x to A[i] (only once).
After this process, we have some array B.
Return the smallest possible difference between the maximum value of B and
the minimum value of B.
Example 1:
Input: A = [1], K = 0 Output: 0 Explanation: B = [1]
Example 2:
Input: A = [0,10], K = 2 Output: 6 Explanation: B = [2,8]
Example 3:
Input: A = [1,3,6], K = 3 Output: 3 Explanation: B = [4,6,3]
Note:
1 <= A.length <= 100000 <= A[i] <= 100000 <= K <= 10000