Commonly used algorithms and data structures in PHP

This article mainly introduces the commonly used algorithms and data structures in PHP. Interested friends can refer to it. I hope it will be helpful to everyone.

<?php  
/**
 * Created by PhpStorm.
 * User: qishou
 * Date: 15-8-2
 * Time: 上午9:12
 */
header("content-type:text/html;charset=utf-8");  
$arr = array(3,5,8,4,9,6,1,7,2);  
echo implode(" ",$arr)."<br/>";  
//---------------------------------------
//              常用排序算法
//---------------------------------------
//冒泡排序
function BubbleSort($arr){  
    $length = count($arr);  
    if($length<=1){  
        return $arr;  
    }  
    for($i=0;$i<$length;$i++){  
        for($j=$length-1;$j>$i;$j--){  
            if($arr[$j]<$arr[$j-1]){  
                $tmp = $arr[$j];  
                $arr[$j] = $arr[$j-1];  
                $arr[$j-1] = $tmp;  
            }  
        }  
    }  
    return $arr;  
}  
echo &#39;冒泡排序：&#39;;  
echo implode(&#39; &#39;,BubbleSort($arr))."<br/>";  

//快速排序
function QSort($arr){  
    $length = count($arr);  
    if($length <=1){  
        return $arr;  
    }  
    $pivot = $arr[0];//枢轴
    $left_arr = array();  
    $right_arr = array();  
    for($i=1;$i<$length;$i++){//注意$i从1开始0是枢轴
        if($arr[$i]<=$pivot){  
            $left_arr[] = $arr[$i];  
        }else{  
            $right_arr[] = $arr[$i];  
        }  
    }  
    $left_arr = QSort($left_arr);//递归排序左半部分
    $right_arr = QSort($right_arr);//递归排序右半部份
    return array_merge($left_arr,array($pivot),$right_arr);//合并左半部分、枢轴、右半部分
}  
echo "快速排序：";  
echo implode(&#39; &#39;,QSort($arr))."<br/>";  

//选择排序(不稳定)
function SelectSort($arr){  
    $length = count($arr);  
    if($length<=1){  
        return $arr;  
    }  
    for($i=0;$i<$length;$i++){  
        $min = $i;  
        for($j=$i+1;$j<$length;$j++){  
            if($arr[$j]<$arr[$min]){  
                $min = $j;  
            }  
        }  
        if($i != $min){  
            $tmp = $arr[$i];  
            $arr[$i] = $arr[$min];  
            $arr[$min] = $tmp;  
        }  
    }  
    return $arr;  
}  
echo "选择排序：";  
echo implode(&#39; &#39;,SelectSort($arr))."<br/>";  

//插入排序
function InsertSort($arr){  
    $length = count($arr);  
    if($length <=1){  
        return $arr;  
    }  
    for($i=1;$i<$length;$i++){  
        $x = $arr[$i];  
        $j = $i-1;  
        while($x<$arr[$j] && $j>=0){  
            $arr[$j+1] = $arr[$j];  
            $j--;  
        }  
        $arr[$j+1] = $x;  
    }  
    return $arr;  
}  
echo &#39;插入排序：&#39;;  
echo implode(&#39; &#39;,InsertSort($arr))."<br/>";  
//---------------------------------------
//              常用查找算法
//---------------------------------------
//二分查找
function binary_search($arr,$low,$high,$key){  
    while($low<=$high){  
        $mid = intval(($low+$high)/2);  
        if($key == $arr[$mid]){  
            return $mid+1;  
        }elseif($key<$arr[$mid]){  
            $high = $mid-1;  
        }elseif($key>$arr[$mid]){  
            $low = $mid+1;  
        }  
    }  
    return -1;  
}  
$key = 6;  
echo "二分查找{$key}的位置：";  
echo binary_search(QSort($arr),0,8,$key);  

//顺序查找
function SqSearch($arr,$key){  
    $length = count($arr);  
    for($i=0;$i<$length;$i++){  
        if($key == $arr[$i]){  
            return $i+1;  
        }  
    }  
    return -1;  
}  
$key = 8;  
echo "<br/>顺序常规查找{$key}的位置：";  
echo SqSearch($arr,$key);  
//---------------------------------------
//              常用数据结构
//---------------------------------------
//线性表的删除(数组实现)
function delete_array_element($arr,$pos){  
    $length = count($arr);  
    if($pos<1 || $pos>$length){  
        return "删除位置出错!";  
    }  
    for($i=$pos-1;$i<$length-1;$i++){  
        $arr[$i] = $arr[$i+1];  
    }  
    array_pop($arr);  
    return $arr;  
}  
$pos = 3;  
echo "<br/>除第{$pos}位置上的元素后：";  
echo implode(&#39; &#39;,delete_array_element($arr,$pos))."<br/>";  

/**
 * Class Node
 * PHP模拟链表的基本操作
 */
class Node{  
    public $data = &#39;&#39;;  
    public  $next = null;  
}  
//初始化
function init($linkList){  
    $linkList->data = 0; //用来记录链表长度
    $linkList->next = null;  
}  
//头插法创建链表
function createHead(&$linkList,$length){  
    for($i=0;$i<$length;$i++){  
        $newNode = new Node();  
        $newNode->data = $i;  
        $newNode->next = $linkList->next;//因为PHP中对象本身就是引用所以不用再可用“&”
        $linkList->next = $newNode;  
        $linkList->data++;  
    }  
}  
//尾插法创建链表
function createTail(&$linkList,$length){  
    $r = $linkList;  
    for($i=0;$i<$length;$i++){  
        $newNode = new Node();  
        $newNode->data = $i;  
        $newNode->next = $r->next;  
        $r->next = $newNode;  
        $r = $newNode;  
        $linkList->data++;  
    }  
}  
//在指定位置插入指定元素
function insert($linkList,$pos,$elem){  
    if($pos<1 && $pos>$linkList->data+1){  
        echo "插入位置错误！";  
    }  
    $p = $linkList;  
    for($i=1;$i<$pos;$i++){  
        $p = $p->next;  
    }  
    $newNode = new Node();  
    $newNode->data = $elem;  
    $newNode->next = $p->next;  
    $p->next = $newNode;  
}  
//删除指定位置的元素
function delete($linkList,$pos){  
    if($pos<1 && $pos>$linkList->data+1){  
        echo "位置不存在！";  
    }  
    $p = $linkList;  
    for($i=1;$i<$pos;$i++){  
        $p = $p->next;  
    }  
    $q = $p->next;  
    $p->next = $q->next;  
    unset($q);  
    $linkList->data--;  
}  
//输出链表数据
function show($linkList){  
    $p = $linkList->next;  
    while($p!=null){  
        echo $p->data." ";  
        $p = $p->next;  
    }  
    echo &#39;<br/>&#39;;  
}  

$linkList = new Node();  
init($linkList);//初始化
createTail($linkList,10);//尾插法创建链表
show($linkList);//打印出链表
insert($linkList,3,&#39;a&#39;);//插入
show($linkList);  
delete($linkList,3);//删除
show($linkList);  

/**
 * Class Stack
 * 用PHP模拟顺序栈的基本操作
 */
class Stack{  
    //用默认值直接初始化栈了，也可用构造方法初始化栈
    private $top = -1;  
    private $maxSize = 5;  
    private $stack = array();  

    //入栈
    public function push($elem){  
        if($this->top >= $this->maxSize-1){  
            echo "栈已满！<br/>";  
            return;  
        }  
        $this->top++;  
        $this->stack[$this->top] = $elem;  
    }  
    //出栈
    public function pop(){  
        if($this->top == -1){  
            echo "栈是空的！";  
            return ;  
        }  
        $elem = $this->stack[$this->top];  
        unset($this->stack[$this->top]);  
        $this->top--;  
        return $elem;  
    }  
    //打印栈
    public function show(){  
        for($i=$this->top;$i>=0;$i--){  
            echo $this->stack[$i]." ";  
        }  
        echo "<br/>";  
    }  
}  

$stack = new Stack();  
$stack->push(3);  
$stack->push(5);  
$stack->push(8);  
$stack->push(7);  
$stack->push(9);  
$stack->push(2);  
$stack->show();  
$stack->pop();  
$stack->pop();  
$stack->pop();  
$stack->show();  

/**
 * Class Deque
 * 使用PHP实现双向队列
 */
class Deque{  
    private $queue = array();  
    public function addFirst($item){//头入队
        array_unshift($this->queue,$item);  
    }  
    public function addLast($item){//尾入队
        array_push($this->queue,$item);  
    }  
    public function removeFirst(){//头出队
        array_shift($this->queue);  
    }  
    public function removeLast(){//尾出队
        array_pop($this->queue);  
    }  
    public  function show(){//打印
        foreach($this->queue as $item){  
            echo $item." ";  
        }  
        echo "<br/>";  
    }  
}  
$deque = new Deque();  
$deque->addFirst(2);  
$deque->addLast(3);  
$deque->addLast(4);  
$deque->addFirst(5);  
$deque->show();  

//PHP解决约瑟夫环问题
//方法一
function joseph_ring($n,$m){  
    $arr = range(1,$n);  
    $i = 0;  
    while(count($arr)>1){  
        $i=$i+1;  
        $head = array_shift($arr);  
        if($i%$m != 0){ //如果不是则重新压入数组
            array_push($arr,$head);  
        }  
    }  
    return $arr[0];  
}  
//方法二
function joseph_ring2($n,$m){  
    $r = 0;  
    for($i=2;$i<=$n;$i++){  
        $r = ($r+$m)%$i;  
    }  
    return $r + 1;  
}  
echo "<br/>".joseph_ring(60,5)."<br/>";  
echo "<br/>".joseph_ring2(60,5)."<br/>";

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php algorithm selection sorting

php algorithm heap sort

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