309 lines
7.8 KiB
PHP
309 lines
7.8 KiB
PHP
<?php
|
||
/**
|
||
* User: lide01
|
||
* Date: 2018/10/9 14:06
|
||
* Desc:
|
||
*/
|
||
|
||
namespace Algo_07;
|
||
require_once '../vendor/autoload.php';
|
||
|
||
use Algo_06\SingleLinkedList;
|
||
|
||
|
||
/**
|
||
* 单链表相关算法
|
||
*
|
||
* Class SingleLinkedListAlgo
|
||
*
|
||
* reverse 单链表反转
|
||
* checkCircle 链表中环的检测
|
||
* mergerSortedList 两个有序的链表合并
|
||
* deleteLastKth 删除链表倒数第n个结点
|
||
* findMiddleNode 求链表的中间结点
|
||
*
|
||
* @package Algo_07
|
||
*/
|
||
Class SingleLinkedListAlgo
|
||
{
|
||
/**
|
||
* 单链表
|
||
*
|
||
* @var
|
||
*/
|
||
public $list;
|
||
|
||
/**
|
||
* 构造函数设置$list
|
||
*
|
||
* SingleLinkedListAlgo constructor.
|
||
*
|
||
* @param SingleLinkedList $list
|
||
*/
|
||
public function __construct(SingleLinkedList $list = null)
|
||
{
|
||
$this->list = $list;
|
||
}
|
||
|
||
/**
|
||
* 设置单链表
|
||
*
|
||
* @param SingleLinkedList $list
|
||
*/
|
||
public function setList(SingleLinkedList $list)
|
||
{
|
||
$this->list = $list;
|
||
}
|
||
|
||
/**
|
||
* 单链表反转
|
||
*
|
||
* 三个指针反转
|
||
* preNode 指向前一个结点
|
||
* curNode 指向当前结点
|
||
* remainNode 指向当前结点的下一个节点（保存未逆序的链表，为了在断开curNode的next指针后能找到后续节点）
|
||
*
|
||
* @return bool
|
||
*/
|
||
public function reverse()
|
||
{
|
||
if (null == $this->list || null == $this->list->head || null == $this->list->head->next) {
|
||
return false;
|
||
}
|
||
|
||
$preNode = null;
|
||
$curNode = $this->list->head->next;
|
||
$remainNode = null;
|
||
|
||
// 保存头结点，稍后指向反转后的链表
|
||
$headNode = $this->list->head;
|
||
// 断开头结点的next指针
|
||
$this->list->head->next = null;
|
||
|
||
while ($curNode != null) {
|
||
$remainNode = $curNode->next;
|
||
$curNode->next = $preNode;
|
||
$preNode = $curNode;
|
||
$curNode = $remainNode;
|
||
}
|
||
|
||
// 头结点指向反转后的链表
|
||
$headNode->next = $preNode;
|
||
|
||
return true;
|
||
}
|
||
|
||
/**
|
||
* 判断链表是否有环
|
||
*
|
||
* 快慢指针判断是否有环
|
||
* @link http://t.cn/ROxpgQ1
|
||
*
|
||
* @return bool
|
||
*/
|
||
public function checkCircle()
|
||
{
|
||
if (null == $this->list || null == $this->list->head || null == $this->list->head->next) {
|
||
return false;
|
||
}
|
||
|
||
$slow = $this->list->head->next;
|
||
$fast = $this->list->head->next;
|
||
|
||
while ($fast != null && $fast->next != null) {
|
||
$fast = $fast->next->next;
|
||
$slow = $slow->next;
|
||
|
||
// 如果慢指针跟快指针相遇了说明有环 解释在上面的链接中
|
||
if ($slow === $fast) {
|
||
return true;
|
||
}
|
||
}
|
||
|
||
return false;
|
||
}
|
||
|
||
/**
|
||
* 合并两个有序链表
|
||
*
|
||
* @param SingleLinkedList $listA
|
||
* @param SingleLinkedList $listB
|
||
*
|
||
* @return SingleLinkedList|\Algo_06\SingleLinkedListNode
|
||
*/
|
||
public function mergerSortedList(SingleLinkedList $listA, SingleLinkedList $listB)
|
||
{
|
||
if (null == $listA) {
|
||
return $listB;
|
||
}
|
||
if (null == $listB) {
|
||
return $listA;
|
||
}
|
||
|
||
$pListA = $listA->head->next;
|
||
$pListB = $listB->head->next;
|
||
$newList = new SingleLinkedList();
|
||
$newHead = $newList->head;
|
||
$newRootNode = $newHead;
|
||
|
||
while ($pListA != null && $pListB != null) {
|
||
if ($pListA->data <= $pListB->data) {
|
||
$newRootNode->next = $pListA;
|
||
$pListA = $pListA->next;
|
||
} else {
|
||
$newRootNode->next = $pListB;
|
||
$pListB = $pListB->next;
|
||
}
|
||
|
||
$newRootNode = $newRootNode->next;
|
||
}
|
||
|
||
// 如果第一个链表未处理完，拼接到新链表后面
|
||
if ($pListA != null) {
|
||
$newRootNode->next = $pListA;
|
||
}
|
||
// 如果第二个链表未处理完，拼接到新链表后面
|
||
if ($pListB != null) {
|
||
$newRootNode->next = $pListB;
|
||
}
|
||
|
||
return $newList;
|
||
}
|
||
|
||
/**
|
||
* 删除链表倒数第n个结点
|
||
*
|
||
* @param $index
|
||
*
|
||
* @return bool
|
||
*/
|
||
public function deleteLastKth($index)
|
||
{
|
||
if (null == $this->list || null == $this->list->head || null == $this->list->head->next) {
|
||
return false;
|
||
}
|
||
|
||
$i = 1;
|
||
$slow = $this->list->head;
|
||
$fast = $this->list->head;
|
||
while ($fast != null && $i < $index) {
|
||
$fast = $fast->next;
|
||
++$i;
|
||
}
|
||
|
||
if (null == $fast) {
|
||
return true;
|
||
}
|
||
|
||
$pre = null;
|
||
while($fast->next != null) {
|
||
$pre = $slow;
|
||
$slow = $slow->next;
|
||
$fast = $fast->next;
|
||
}
|
||
|
||
if (null == $pre) {
|
||
$this->list->head->next = $slow->next;
|
||
} else {
|
||
$pre->next = $pre->next->next;
|
||
}
|
||
|
||
return true;
|
||
}
|
||
|
||
/**
|
||
* 寻找中间节点
|
||
*
|
||
* 快慢指针遍历
|
||
*
|
||
* @return \Algo_06\SingleLinkedListNode|bool|null
|
||
*/
|
||
public function findMiddleNode()
|
||
{
|
||
if (null == $this->list || null == $this->list->head || null == $this->list->head->next) {
|
||
return false;
|
||
}
|
||
|
||
$slow = $this->list->head->next;
|
||
$fast = $this->list->head->next;
|
||
|
||
while ($fast != null && $fast->next != null) {
|
||
$fast = $fast->next->next;
|
||
$slow = $slow->next;
|
||
}
|
||
|
||
return $slow;
|
||
}
|
||
}
|
||
|
||
echo '---------------------- 单链表反转 ----------------------' . PHP_EOL . PHP_EOL;
|
||
$list = new SingleLinkedList();
|
||
$list->insert(1);
|
||
$list->insert(2);
|
||
$list->insert(3);
|
||
$list->insert(4);
|
||
$list->insert(5);
|
||
$list->insert(6);
|
||
$list->insert(7);
|
||
|
||
// 单链表反转
|
||
$listAlgo = new SingleLinkedListAlgo($list);
|
||
$listAlgo->list->printList();
|
||
$listAlgo->reverse();
|
||
$listAlgo->list->printList();
|
||
echo '--------------------------------------------------------' . PHP_EOL . PHP_EOL;
|
||
|
||
echo '---------------------- 链表中环的检测 ----------------------'. PHP_EOL . PHP_EOL;
|
||
// 链表中环的检测
|
||
$listCircle = new SingleLinkedList();
|
||
$listCircle->buildHasCircleList();
|
||
$listAlgo->setList($listCircle);
|
||
var_dump($listAlgo->checkCircle());
|
||
echo '------------------------------------------------------------' . PHP_EOL . PHP_EOL;
|
||
|
||
echo '---------------------- 两个有序的链表合并 ----------------------' . PHP_EOL . PHP_EOL;
|
||
// 两个有序的链表合并
|
||
$listA = new SingleLinkedList();
|
||
$listA->insert(9);
|
||
$listA->insert(7);
|
||
$listA->insert(5);
|
||
$listA->insert(3);
|
||
$listA->insert(1);
|
||
$listA->printList();
|
||
|
||
$listB = new SingleLinkedList();
|
||
$listB->insert(10);
|
||
$listB->insert(8);
|
||
$listB->insert(6);
|
||
$listB->insert(4);
|
||
$listB->insert(2);
|
||
$listB->printList();
|
||
|
||
$listAlgoMerge = new SingleLinkedListAlgo();
|
||
$newList = $listAlgoMerge->mergerSortedList($listA, $listB);
|
||
$newList->printListSimple();
|
||
echo '----------------------------------------------------------------'. PHP_EOL . PHP_EOL;
|
||
|
||
echo '---------------------- 删除链表倒数第n个结点 ----------------------' . PHP_EOL . PHP_EOL;
|
||
// 删除链表倒数第n个结点
|
||
$listDelete = new SingleLinkedList();
|
||
$listDelete->insert(1);
|
||
$listDelete->insert(2);
|
||
$listDelete->insert(3);
|
||
$listDelete->insert(4);
|
||
$listDelete->insert(5);
|
||
$listDelete->insert(6);
|
||
$listDelete->insert(7);
|
||
$listDelete->printList();
|
||
$listAlgo->setList($listDelete);
|
||
$listAlgo->deleteLastKth(3);
|
||
var_dump($listAlgo->list->printListSimple());
|
||
echo '------------------------------------------------------------------'. PHP_EOL . PHP_EOL;
|
||
|
||
echo '---------------------- 求链表的中间结点 ----------------------' . PHP_EOL . PHP_EOL;
|
||
// 求链表的中间结点
|
||
$listAlgo->setList($list);
|
||
$middleNode = $listAlgo->findMiddleNode();
|
||
var_dump($middleNode->data);
|
||
echo '-------------------------------------------------------------'. PHP_EOL . PHP_EOL;
|