二分法查找算法 順序查找算法的PHP代碼

jspet 9年前發布 | 1K 次閱讀 PHP 

<?php
/**


    

  • 查找
*
**/
// 順序查找
function normal_search($arrData,$val) {
$len = count($arrData);
if($len == 0) return -1;
for($i = 0;$i < $len; $i++ ) {

    echo "find No.",$i + 1," value = ",$arrData[$i]," is = ",$val,"? <br/>";
// 找到了
if($arrData[$i] == $val) return $i;

    
}
return -1;
}
    • 



// 測試順序查找
$arrData = array(4,51,6,73,2,5,9,33,50,3,4,6,1,4,67);
echo normal_search($arrData,6),"<br/>";
echo normal_search($arrData,66),"<br/>";


// 二分法查找(針對有序的列進行查找)
function binary_search($arrData,$val) {
    $len = count($arrData);
    if($len == 0) return -1;



$start = 0;
$end   = $len - 1;

while($start <= $end) {
    $middle = intval(($start + $end)/2);
    echo "start = ",$start," end = ",$end," middle = ",$middle,"<br/>";
    if($arrData[$middle] == $val) {
        return $middle;
    } elseif ($arrData[$middle] > $val) {
        $end = $middle - 1 ;
    } elseif ($arrData[$middle] < $val) {
        $start = $middle + 1;
    }
}
return -1;



}


// 測試一下二分法查找
$arrData = array(1,2,3,4,5,7,8,9,11,23,56,100,104,578,1000);
echo binary_search($arrData,578),"<br/>";
echo binary_search($arrData,66),"<br/>";</pre>
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