package main

import (
	"fmt"
	"leetcode-golang/entity"
)

func mergeTwoLists(l1 *entity.ListNode, l2 *entity.ListNode) *entity.ListNode {
	head := &entity.ListNode{
		Val:  -1,
		Next: nil,
	}

	pre := head

	for l1 != nil && l2 != nil {
		if l1.Val <= l2.Val {
			pre.Next = l1
			l1 = l1.Next
		} else {
			pre.Next = l2
			l2 = l2.Next
		}
		pre = pre.Next
	}
	if l1 != nil {
		pre.Next = l1
	} else {
		pre.Next = l2
	}
	return head.Next
}

func main() {
	head1 := &entity.ListNode{
		Val: 1,
		Next: &entity.ListNode{
			Val: 3,
		},
	}

	head2 := &entity.ListNode{
		Val: 2,
		Next: &entity.ListNode{
			Val: 4,
		},
	}
	head := mergeTwoLists(head1, head2)
	for head != nil {
		fmt.Println(head.Val)
		head = head.Next
	}
}