910. Smallest Range II

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. `1 <= A.length <= 10000`
2. `0 <= A[i] <= 10000`
3. `0 <= K <= 10000`

910. Smallest Range II
``````struct Solution;

impl Solution {
fn smallest_range_ii(mut a: Vec<i32>, k: i32) -> i32 {
let n = a.len();
a.sort_unstable();
let mut max = a[n - 1];
let mut min = a[0];
let mut res = max - min;
for i in 0..n - 1 {
max = max.max(a[i] + 2 * k);
min = a[i + 1].min(a[0] + 2 * k);
res = res.min(max - min);
}
res
}
}

#[test]
fn test() {
let a = vec![1];
let k = 0;
let res = 0;
assert_eq!(Solution::smallest_range_ii(a, k), res);
let a = vec![0, 10];
let k = 2;
let res = 6;
assert_eq!(Solution::smallest_range_ii(a, k), res);
let a = vec![1, 3, 6];
let k = 3;
let res = 3;
assert_eq!(Solution::smallest_range_ii(a, k), res);
let a = vec![2, 7, 2];
let k = 1;
let res = 3;
assert_eq!(Solution::smallest_range_ii(a, k), res);
}
``````