二分查找

python

# *_*coding:utf-8 *_*
def binaery_search(list,item):
    low=0
    high=len(list)-1

    while low <= high:
        mid=int((low+high)/2)
        guess=list[mid]
        if guess == item:
            return mid
        if guess >item:
            high=mid-1
        else:
            low=mid+1
    return None


my_list=[1,3,5,7,9,11]

print(binaery_search(my_list,1))
print(binaery_search(my_list,3))
print(binaery_search(my_list,5))
print(binaery_search(my_list,7))
print(binaery_search(my_list,9))
print(binaery_search(my_list,11))
print(binaery_search(my_list,-1))

php代码

<?php
//二分查找法
function binSearch($arr,$search){
    $height=count($arr)-1;
    $low=0;
    while($low<=$height){
        $mid=floor(($low+$height)/2);//获取中间数
        echo $mid;
        if($arr[$mid]==$search){
            return $mid;//返回
        }elseif($arr[$mid]<$search){//当中间值小于所查值时，则$mid左边的值都小于$search，此时要将$mid赋值给$low
            $low=$mid+1;
        }elseif($arr[$mid]>$search){//中间值大于所查值,则$mid右边的所有值都大于$search,此时要将$mid赋值给$height
            $height=$mid-1;
        }
    }
    return "查找失败";
}
//二分查找递归实现
function binSearch2($arr,$low,$height,$k){
    if($low<=$height){
        $mid=floor(($low+$height)/2);//获取中间数
        var_dump($low.$height);
        echo "<br>";
        var_dump($mid);
        if($arr[$mid]==$k){
            return $mid;
        }elseif($arr[$mid]<$k){
            return binSearch2($arr,$mid+1,$height,$k);
        }elseif($arr[$mid]>$k){
            return binSearch2($arr,$low,$mid-1,$k);
        }
    }
    return -1;
}

//顺序查找
function seqSearch($arr,$k){
    foreach($arr as $key=>$val){
        if($val==$k){
            return $key;
        }
    }
    return -1;
}

$arr=array(1,2,3,4);
$res = binSearch2($arr,0,4,4);
var_dump($res);