BM13 判断一个链表是否为回文结构

描述

给定一个链表，请判断该链表是否为回文结构。回文是指该字符串正序逆序完全一致。```

{2,1}
false

{1,2,2,1}
true

题解

使用快慢指针

package main

import (
	. "nc_tools"
)

/*
 * type ListNode struct{
 *   Val int
 *   Next *ListNode
 * }
 */

/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 *
 * @param head ListNode类 the head
 * @return bool布尔型
 */
func isPail(head *ListNode) bool {
	if head == nil||head.Next==nil{
		return true
	}
    var slow,fast,nowNode *ListNode
    nowNode=head
    slow=head
    fast=head.Next
	for fast!=nil&&fast.Next!=nil{
        slow=slow.Next
        fast=fast.Next.Next
    }
    resHead:=reserve(slow.Next)
    for resHead.Next!=nil{
        if nowNode.Val!=resHead.Val{
            return false
        }
        nowNode=nowNode.Next
        resHead=resHead.Next
    }
    return true
}
func reserve(head *ListNode) *ListNode {
	var per, now, next *ListNode
	now = head
	next = head
	for now != nil {
		next = now.Next
		now.Next = per
		per = now
		now = next
	}
	return per
}

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