PHP二分查找算法

二分查找法

<?php
//循环方式
function binary($arr, $low, $top, $target) {

    while ($low <= $top) {
        $mid = floor(($low + $top) / 2);
        if ($arr[$mid] == $target) {
            return $mid;
        } elseif($arr[$mid] < $target) {
            $low = $mid + 1;
        } else {
            $top = $mid - 1;
        }
    }
    return -1;
}

$arr = array(1,3,9,23,54);
echo binary($arr, 0, count($arr), 9);

//递归方式
function binaryRecursive($arr, $low, $top, $target) {
    if ($low <= $top) {
        $mid = floor(($low + $top) / 2);
		if ($arr[$mid] == $target) {
			return $mid;
		} elseif ($arr[$mid] < $target) {
            $low = $mid + 1;
            return binaryRecursive($arr, $low, $top, $target);
        } else {
            $top = $mid - 1;
            return binaryRecursive($arr, $low, $top, $target);
        }
    } else {
        return -1;
    }
}

$arr = array(1,3,9,23,54);
echo binaryRecursive($arr, 0, count($arr), 9);