1669 - Merge In Between Linked Lists\.

Medium

You are given two linked lists: list1 and list2 of sizes n and m respectively.

Remove list1's nodes from the <code>a^th</code> node to the <code>b^th</code> node, and put list2 in their place.

The blue edges and nodes in the following figure indicate the result:

Build the result list and return its head.

Example 1:

Input: list1 = 0,1,2,3,4,5, a = 3, b = 4, list2 = 1000000,1000001,1000002

Output: 0,1,2,1000000,1000001,1000002,5

Explanation: We remove the nodes 3 and 4 and put the entire list2 in their place.

The blue edges and nodes in the above figure indicate the result.

Example 2:

Input: list1 = 0,1,2,3,4,5,6, a = 2, b = 5, list2 = 1000000,1000001,1000002,1000003,1000004

Output: 0,1,1000000,1000001,1000002,1000003,1000004,6

Explanation: The blue edges and nodes in the above figure indicate the result.

Constraints:

• <code>3 <= list1.length <= 10⁴</code>

• 1 <= a <= b < list1.length - 1

• <code>1 <= list2.length <= 10⁴</code>