这样写二分查找如何不对呢 -PHP Tutorial-php.cn

这样写二分查找如何不对呢

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Release： 2016-06-13 12:47:28

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这样写二分查找怎么不对呢

<br />
<php <br />
function binarySearch($arr,$a){<br />
    <br />
    $low = 0;<br />
    $high = count($arr)-1;<br />
    $mid = ceil(($low+$high)/2);<br />
<br />
while($low<=$high){<br />
<br />
    if($a==$arr[$mid]){<br />
    	echo "查找的数的位置是第"."$mid";<br />
    }<br />
<br />
    if($a>$arr[$mid]){<br />
<br />
        $high = count($arr)-1;<br />
    	$low = $mid+1;<br />
	    $mid = ceil(($low+$high)/2);<br />
    }<br />
<br />
    if ($a<$arr[$mid]) {<br />
    	<br />
    	$low = 0;<br />
    	$high = $mid-1;<br />
    	$mid = ceil(($low+$high)/2);<br />
    }<br />
  }<br />
}<br />
$arr1 = array(5,7,9,10,12,16,19);<br />
binarySearch($arr1,12);<br />
<br />
?>

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------解决方案--------------------

本帖最后由 xuzuning 于 2013-03-30 17:42:33 编辑

function binarySearch($arr,$a){<br />
  $low = 0;<br />
  $high = count($arr)-1;<br />
  $mid = ceil(($low+$high)/2);<br />
  $num = count($arr);<br />
  while($low<=$high && $num--){<br />
    if($a==$arr[$mid]){<br />
      echo "查找的数的位置是第"."$mid";<br />
      break;<br />
    }<br />
    list($low, $high) = $a > $arr[$mid] ? array($mid, $high) : array($low, $mid);<br />
    $mid = ceil(($low+$high)/2);<br />
  }<br />
}<br />

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------解决方案--------------------

Related labels：

arr mid nbsp

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