Double a Number Represented as a Linked List

Medium

Given the head of a non-empty linked list whose nodes store the digits of a non-negative integer in order (most significant digit first, no leading zeros except the number 0 itself), return the list representing double that number.

Example 1

Input:  head = [1,8,9]
Output: [3,7,8]
Explanation: 189 * 2 = 378.

Example 2

Input:  head = [9,9,9]
Output: [1,9,9,8]

Constraints

• 1 <= number of nodes <= 6
• 0 <= Node.val <= 9
• No leading zeros except the number 0.