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A brief discussion on how to implement and process linked lists in PHP

青灯夜游
青灯夜游 forward
2021-03-02 18:02:27 2115browse

This article will introduce to you how to implement and process linked lists in PHP. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

A brief discussion on how to implement and process linked lists in PHP

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Linked List

A linked list is a non-continuous and non-sequential storage structure on a physical storage unit. The logical order of data elements is realized through the link order of pointers in the linked list. A linked list consists of a series of nodes (each element in the linked list is called a node), and nodes can be dynamically generated at runtime.

Forms: single linked list, double linked list, skip list (the redis collection data structure is realized by skip list, time complexity O (log N))

Learn about skip list: https://lotabout .me/2018/skip-list/

php implements the add, delete, modify and query operations on the linked list

Define node class:

val = $val; $this->next = $next; } }

Linked list class:

head = new Node(); $this->size = 0; } //头插法 public function addFirst( $value ){ // $node = new Node($value); // $node->next = $this->head; // $this->head = $node; //简化 // $this->head = new Node( $value, $this->head ); // $this->size++; $this->add(0,$value); } /**指定索引位置插入 * @param $index * @param $value * @throws Exception */ public function add( $index, $value ){ if( $index > $this->size ) throw new Exception('超过链表范围'); // if( $index==0 ){ // $this->addFirst($value); // }else{ $prev = $this->head; for($i=0;$inext; } // $node = new Node($value); // $node->next = $prev->next; // $prev->next = $node; $prev->next = new Node($value,$prev->next); // } $this->size++; } /**尾插法 * @param $value */ public function addLast( $value ){ $this->add($this->size,$value); } /*** * 编辑 * @param $index * @param $value * @throws Exception */ public function edit( $index, $value ){ if( $index > $this->size-1 ) throw new Exception('超过链表范围'); $prev = $this->head->next; for($i=0;$ival = $value; $prev = $prev->next; } } /** * 查询 * @param $index * @return null * @throws Exception */ public function select($index){ if( $index > $this->size-1 ) throw new Exception('超过链表范围'); $prev = $this->head->next; for($i=0;$inext; } } /**删除 * @param $index * @throws Exceptionr */ public function delete( $index ){ if( $index > $this->size-1 ) throw new Exception('超过链表范围'); $prev = $this->head; for($i=0;$inext = $prev->next->next; $prev = $prev->next; } $this->size--; } /**检索值是否存在 * @param $value * @return bool */ public function iscontain( $value ){ $prev = $this->head->next; while( $prev ){ if( $prev->val==$value ){ return true; } $prev = $prev->next; } return false; } /**转换为字符串 * @return string */ public function tostring(){ $prev = $this->head->next; $r = []; while( $prev ){ $r[] = $prev->val; $prev = $prev->next; } return implode('->',$r); } /** * 删除指定的节点值 * @param $value */ public function removeFileds( $value ){ $prev = $this->head; while( $prev->next ){ if( $prev->val == $value ){ $prev->val = $prev->next->val; $prev->next = $prev->next->next; }else{ $prev = $prev->next; } } } /** * 通过递归方式删除指定的节点值 * @param $value */ public function removeFiledsByRecursion( $value ){ $this->head = $this->removeByRecursion( $this->head ,$value); return $this->head; } public function removeByRecursion( $node , $value, $level=0 ){ if( $node->next == null ){ $this->showDeeep($level,$node->val); return $node->val == $value ? $node->next:$node; } $this->showDeeep($level,$node->val); $node->next = $this->removeByRecursion( $node->next,$value,++$level ); $this->showDeeep($level,$node->val); return $node->val == $value ? $node->next:$node; } /** * 显示深度 * 帮助理解递归执行过程,回调函数执行层序遵循系统栈 * @param int $level 深度层级 * @param $val * @return bool */ public function showDeeep( $level=1,$val ){ if( $level

The calling operation is as follows:

addFirst(1); $node->add(1,7); $node->add(2,10); $node->edit(1,8); var_dump($node->select(1)) ; $node->delete(1); $node->addLast(99); var_dump($node->iscontain(2)); var_export($node); var_export($node->tostring());

Analyze the time complexity of the linked list operation:

增: O(n) 只对链表头操作:O(1) 删: O(n) 只对链表头操作:O(1) 改:O(n) 查:O(n) 只对链表头操作:O(1)

Use the linked list to implement the stack

addFirst($value); } /** * @return mixed */ public function pop(){ $r = $this->head->next->val; $this->delete(0); return $r; } }
push(1); $stack->push(3); $stack->push(6); $stack->push(9); print_r($stack->pop()); print_r($stack->head);

Linked list implementation queue

A brief discussion on how to implement and process linked lists in PHP

head->val==null ){ $this->tail = new Node( $value ); $this->head = $this->tail; }else{ $this->tail->next = new Node( $value ); $this->tail = $this->tail->next; } $this->size++; } /** * pop * @return null * @throws \Exception */ public function pop(){ if( $this->sizehead->val; $this->head = $this->head->next; $this->size--; return $val; } /** * 查看队首 */ public function checkHead(){ return $this->head->val; } /** * 查看队尾 */ public function checkEnd(){ return $this->tail->val; } /** * toString */ public function toString(){ $r = []; while( $this->head ){ $r[] = $this->head->val; $this->head = $this->head->next; } return implode('->',$r); } }

Test

push(1); $stack->push(3); $stack->push(6); $stack->push(9); print_r($stack->pop()); print_r($stack->head); print_r($stack->checkHead()); print_r($stack->checkEnd()); print_r($stack->toString()); /** 1 app\models\Node Object ( [val] => 3 [next] => app\models\Node Object ( [val] => 6 [next] => app\models\Node Object ( [val] => 9 [next] => ) ) ) 3 9 3->6->9 **/

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