package top100liked

import (
	"fmt"
	"testing"
)

// https://leetcode.cn/problems/reverse-linked-list/description/?envType=study-plan-v2&envId=top-100-liked

type ListNode struct {
	Val  int
	Next *ListNode
}

func reverseList(head *ListNode) *ListNode {
	if head == nil {
		return nil
	}
	var last *ListNode = nil
	h := head
	for h.Next != nil {
		tmp := h.Next
		h.Next = last
		last = h
		h = tmp
	}
	h.Next = last
	return h
}

func TestS23(t *testing.T) {
	input := ListNode{
		Val: 1,
		Next: &ListNode{
			Val: 2,
			Next: &ListNode{
				Val: 3,
				Next: &ListNode{
					Val: 4,
					Next: &ListNode{
						Val:  5,
						Next: nil,
					},
				},
			},
		},
	}
	output := reverseList(&input)

	for output.Next != nil {
		fmt.Println(output.Val)
		output = output.Next
	}
	fmt.Println(output.Val)
}