php 二分查找法

递归二分

<?php
/**
 * @param $target 查找目标
 * @param $arr 待查找数组
 * @param $start 数组起始索引
 * @param $end 数组结束索引
 * @return String
 */
function BinarySearch($target,$arr,$start,$end){
    if ($start>$end){
        return "Sorry, No Result!";
    }
    $mid = intval($start+($end-$start)/2);

   
    if ($target == $arr[$mid])
        return $mid;
    if ($target<$arr[$mid])
        return BinarySearch($target,$arr,$start,$mid-1);
    else
        return BinarySearch($target,$arr,$mid+1,$end);
}

$arr = [0=>'张三',1=>'李四',2=>'王二',3=>'马志'];
echo BinarySearch('李四',$arr,0,sizeof($arr));

循环二分

<?php
/**
 * @param $target 查找目标
 * @param $arr  待查找数组
 * @return String
 */
function BinarySearch($target,$arr)
{
    $start = 0;
    $end = count($arr) - 1;
    while ($start <= $end)
    {
        $mid = intval($start + ($end - $start)/2);
        if ($target == $arr[$mid])
            return $mid;
        if ($target < $arr[$mid])
            $end = $mid - 1;
        else
            $start = $mid + 1;
    }
    return "Sorry, No Resustartt!";
}

$arr = [0=>'张三',1=>'李四',2=>'王二',3=>'马志'];
echo BinarySearch('王二',$arr);