/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} x
 * @return {ListNode}
 */
var partition = function (head, x) {
    const d1 = new ListNode();
    const d2 = new ListNode();
    let t1 = d1,
        t2 = d2;
    while (head) {
        if (head.val < x) {
            t1.next = head;
            t1 = t1.next;
        } else {
            t2.next = head;
            t2 = t2.next;
        }
        head = head.next;
    }
    t1.next = d2.next;
    t2.next = null;
    return d1.next;
};