https://leetcode.com/problems/partition-list/
Given the head of a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.
You should preserve the original relative order of the nodes in each of the two partitions.
Example 1:
Input: head = [1,4,3,2,5,2], x = 3 Output: [1,2,2,4,3,5] Example 2:
Input: head = [2,1], x = 2 Output: [1,2]
Constraints:
The number of nodes in the list is in the range [0, 200]. -100 <= Node.val <= 100 -200 <= x <= 200