數據結構之隊列——順序存儲結構（php代碼實現——方法三）

<?php
/**
 * 第三種——循環順序隊列的實現方法
 * 此方法是解決前兩種方法的缺點，利用循環隊列的方法達到了最優時間復雜度和空間復雜度
 *
 *
 */
class SqQueue3{
    const ARR_MAX=20;
    private $SqArr;
    private $front;
    private $rear;

    //初始化隊列
    public function __construct(){
        $this->SqArr=array();
        $this->front=0;
        $this->rear=0;
    }

    //銷毀隊列
    public function DestroyQueue(){
        $this->SqArr=null;
        $this->front=$this->rear=0;
    }

    //清空隊列
    public function ClearQueue(){
        $this->SqArr=array();
        $this->front=$this->rear=0;
    }

    //隊列是否為空
    public function QueueEmpty(){
        if($this->front==$this->rear){
            return 'Null';
        }else{
            return 'No Null';
        }
    }

    //隊列的長度
    public function QueueLength(){
        return ($this->rear - $this->front + self::ARR_MAX) % self::ARR_MAX;
    }

    //取得隊頭元素
    public function GetHead(){
        if($this->rear==$this->front){
            return 'ERROR';
        }
        return $this->SqArr[$this->front];
    }

    //從隊尾摻入元素
    public function EnQueue($elem){
        $tail=($this->rear + 1)%self::ARR_MAX;//如果此值等于頭元素說明隊列已滿
        if($tail == $this->front){
            return 'ERROR';
        }
        $this->SqArr[$this->rear]=$elem;
        $this->rear=($this->rear+1)%self::ARR_MAX;
        return 'OK';
    }

    //從隊頭刪除元素
    public function DeQueue(){
        if($this->rear==$this->front){
            return 'ERROR';
        }
        unset($this->SqArr[$this->front]);
        $this->front=($this->front + 1)%self::ARR_MAX;
        return 'OK';
    }

    //遍歷隊元素
    public function QueueTraverse(){
        $arr=array();
        for($i=0;$i<self::ARR_MAX;$i++){
            if(isset($this->SqArr[$i])){
                $arr[]=$this->SqArr[$i];
            }
        }
        return $arr;
    }
    //或者
    public function QueueTraverse2(){
        $arr=array();
        $i=$this->front;
        while($i != $this->rear){
            $arr[]=$this->SqArr[$i];
            $i=($i+1)%self::ARR_MAX;
        }
        return $arr;
    }
}