package mergesorted

type ListNode struct {
	Val  int
	Next *ListNode
}

func reverse(list *ListNode) *ListNode {
	var result *ListNode
	for list != nil {
		result = &ListNode{Val: list.Val, Next: result}
		list = list.Next
	}

	return result
}

func mergeTwoLists(list1 *ListNode, list2 *ListNode) *ListNode {

	var result *ListNode
	for list1 != nil || list2 != nil {
		if list1 == nil {
			result = &ListNode{Val: list2.Val, Next: result}
			list2 = list2.Next
		} else if list2 == nil {
			result = &ListNode{Val: list1.Val, Next: result}
			list1 = list1.Next
		} else if list1.Val < list2.Val {
			result = &ListNode{Val: list1.Val, Next: result}
			list1 = list1.Next
		} else {
			result = &ListNode{Val: list2.Val, Next: result}
			list2 = list2.Next
		}
	}

	return reverse(result)
}

func MergeTwoLists(list1 *ListNode, list2 *ListNode) *ListNode {
	return mergeTwoLists(list1, list2)
}