Merge Two Sorted Lists

Given the heads of two sorted linked lists list1 and list2, merge the two lists into one sorted list by splicing together nodes from both lists.

Return the head of the merged linked list.

Examples

Example 1:

Input: l1 = [1,2,4], l2 = [1,3,4]

Output: [1,1,2,3,4,4]

Explanation: Merging [1→2→4] and [1→3→4] produces [1→1→2→3→4→4].

Example 2:

Input: l1 = [], l2 = []

Output: []

Explanation: Both lists are empty so the result is also empty.

Example 3:

Input: l1 = [], l2 = [0]

Output: [0]

Explanation: One list is empty so the result is the other list.

Constraints

• The number of nodes in both lists is in the range [0, 50].
• -100 <= Node.val <= 100
• Both list1 and list2 are sorted in non-decreasing order.