算法之二分查找(php版实现+测试)

来源：互联网发布：港融大数据平台编辑：程序博客网时间：2024/05/16 01:20

递归版二分查找：
核心算法:binarysearch.php
//echo内容均为debug

<?php   //递归    function Rank($key,&$array,$lo,$hi,$deep)    {        if ($lo > $hi)        {            echo "$key 未找到<br/>";            return -1;        }        //php是弱类型 利用floor向下取整(数组中会自动取整可不需要)        $mid = floor($lo + ($hi - $lo) / 2);        echo "deep: ".$deep." lo: ".$lo." hi:".$hi.'<br/>';        if ($array[$mid] > $key)        {            ++$deep;            return Rank($key,$array,$lo,$mid - 1,$deep);        }        else if ($array[$mid] < $key)        {            ++$deep;            return Rank($key,$array,$mid + 1,$hi,$deep);        }        else        {            echo "$key 已找到<br/>";            return $mid;        }    }    function BinarySearch($key,&$array)    {        $deep = 0;        sort($array);        return Rank($key,$array,0,count($array) - 1,$deep);    }?>

测试代码+界面：totest.php

<?php    include("binarysearch.php");   echo    '<html>            <body>                    <form ENCTYPE = "multipart/form-data" action = "totest.php" method ="post" align = "center">                        查找:<input type = "text" name = "key"><br>                        文件名:<input type = "file" name = "marco" value = ""><br>                        <input type = "submit" value = "开始">                    </form>            </body>    </html>';    function test($key,$file,$tmp)    {        $ex = explode(".",$file);        $suffix = array_pop($ex);        if($suffix != "txt")            exit(0);        $data = file_get_contents($tmp);        $lines = explode("\r\n",$data);        $array = array();        foreach ($lines as $words)        {            $line = explode(' ',$words);            foreach ($line as $word)                $array[] = $word;        }        BinarySearch($key,$array);    }    test($_POST['key'],$_FILES['marco']['name'],$_FILES['marco']['tmp_name']);?>

运行:
这里写图片描述

非递归版:
核心算法:bianrysearch.php

<?php    function BinarySearch($key,&$array)    {        sort($array);        $lo = 0;        $hi = count($array) - 1;        while ($lo <= $hi)        {            $mid = floor($lo + ($hi - $lo) / 2);            if ($array[$mid] > $key)                $hi = $mid - 1;            else if ($array[$mid] < $key)                $lo = $mid + 1;            else                {                    //debuging                    echo "$key 已找到<br/>";                    return $mid;                }        }        echo "$key 未找到<br/>";        return -1;    }?>

totest.php与上面相同:
实现:
这里写图片描述

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