function mergeLists(headone, headtwo) { if (headone === null || headtwo === null) { return headone === null ? headtwo : headone } let p1 = headone.val <= headtwo.val ? headone : headtwo let p2 = p1 === headone ? headtwo : headone const head = p1 head.next = mergeLists(p1.next, p2) return head }