<php
function binarySearch($arr,$a){
$low = 0;
$high = count($arr)-1;
$mid = ceil(($low+$high)/2);
while($low<=$high){
if($a==$arr[$mid]){
echo "查找的数的位置是第"."$mid";
}
if($a>$arr[$mid]){
$high = count($arr)-1;
$low = $mid+1;
$mid = ceil(($low+$high)/2);
}
if ($a<$arr[$mid]) {
$low = 0;
$high = $mid-1;
$mid = ceil(($low+$high)/2);
}
}
}
$arr1 = array(5,7,9,10,12,16,19);
binarySearch($arr1,12);
?>
------解决方案--------------------
function binarySearch($arr,$a){
$low = 0;
$high = count($arr)-1;
$mid = ceil(($low+$high)/2);
$n = 0;防止死循环的措施
while($low<=$high && $n++<count($arr)){
if($a==$arr[$mid]){
echo "查找的数的位置是第"."$mid";
break;
}
if($a>$arr[$mid]){
$high = count($arr)-1;
$low = $mid-1;//注意这里
$mid = ceil(($low+$high)/2);
}
if ($a<$arr[$mid]) {
$low = 0;
$high = $mid+1;//注意这里
$mid = ceil(($low+$high)/2);
}
}
}
------解决方案--------------------
按 php 实际可写作
function binarySearch($arr,$a){
$low = 0;
$high = count($arr)-1;
$mid = ceil(($low+$high)/2);
$num = count($arr);
while($low<=$high && $num--){
if($a==$arr[$mid]){
echo "查找的数的位置是第"."$mid";
break;
}
list($low, $high) = $a > $arr[$mid] ? array($mid, $high) : array($low, $mid);
$mid = ceil(($low+$high)/2);
}
}
------解决方案--------------------