一个有序的数组,用二分查找法查找出某个值的位置。分别用递归和非递归两种方法:
递归:
function search_arr($arr,$low,$hight,$m){
if($low <= $hight){
$mid = intval(($low+$hight) / 2);
if($arr[$mid] == $m){
return $mid;
}else{
if($arr[$mid] > $m){
return search_arr($arr,$low,$mid-1,$m);
}else{
return search_arr($arr,$mid+1,$hight,$m);
}
}
}else{
return false;
}
}
非递归
function search_arr1($arr,$m){
$low = 0;
$hight = count($arr)-1;
while($low <= $hight){
$mid = intval(($low + $hight)/2);
if($arr[$mid] == $m){
return $mid;
}else{
if($arr[$mid]>$m){
$hight = $mid - 1;
}else{
$low = $mid +1;
}
}
}
}
$arr = array(1,3,5,7,9,21,34);
$hight = count($arr) -1;
$re = search_arr($arr,0,$hight,50);
$re = search_arr1($arr,3);