Smallest Range Covering Elements from K Lists

You have `k` lists of sorted integers in **non-decreasing order**. Find the smallest range that includes at least one number from each of the `k` lists. We define the range `[a, b]` is smaller than range `[c, d]` if `b - a < d - c` **or** `a < c` if `b - a == d - c`.   **Example 1:** **Input:** nums = [[4,10,15,24,26],[0,9,12,20],[5,18,22,30]] **Output:** [20,24] **Explanation: ** List 1: [4, 10, 15, 24,26], 24 is in range [20,24]. List 2: [0, 9, 12, 20], 20 is in range [20,24]. List 3: [5, 18, 22, 30], 22 is in range [20,24]. ``` **Example 2:** **Input:** nums = [[1,2,3],[1,2,3],[1,2,3]] **Output:** [1,1] ```   **Constraints:** - `nums.length == k` - `1 <= k <= 3500` - `1 <= nums[i].length <= 50` - `-105 <= nums[i][j] <= 105` - `nums[i]` is sorted in **non-decreasing** order.