I found an interesting problem on https://leetcode.com/problems/smallest-range-i/:
Given an array A of integers, for each integer A[i] we may choose any x with -K <= x <= K, and add x to A[i].
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: 0
Explanation: B = [3,3,3] or B = [4,4,4]

 
Note:

1 <= A.length <= 10000
0 <= A[i] <= 10000
0 <= K <= 10000

I tried it in Python, but could not do it. Can you solve it?
class Solution:
    def smallestRangeI(self, a: List[int], k: int) -> int:
        a = sorted(a)
        a[-1] = max(a)
        a[0]= min(a)
        #print(a,a[-1])
        if a[-1]-k<=(a[0]+k):
            return 0
        return  (a[-1]-k)-(a[0]+k)