10个小球用天平找出重量不同的那个

<?php

$data = array(0, 0, 0, 0, 1, 0, 0, 0, 0, 0);

class filterBall {
    public $theSpecial; //特殊球 1 = 重, -1 = 轻
    public $balanceTimes = 0;
    /*
     * param integer & array $left 左边的球
     * param integer & array $right 右边的球
     * return 左边的球重=-1 相同重=0 右边球重=1
     */
    public function balance($left, $right) {
        $this->balanceTimes++;
        if (is_array($left)) {
            $left = array_sum($left);
        }
        if (is_array($right)) {
            $right = array_sum($right);
        }
        if ($left == $right) {
            return 0;
        } elseif ($left > $right) {
            return -1;
        } else {
            return 1;
        }
    }

    function execute($data) {
        $mod = intval(count($data) / 3); //取模
        // 将数组切分成3 - 4个每个有$mod个元素的数组
        $i = 0;
        $j = 0;
        $newArray = array();
        while($i < count($data)) {
            if (isset($newArray[$j]) && count($newArray[$j]) >= $mod) {
                $j++;
            }
            $newArray[$j][] = $data[$i];
            $i++;
        }

        $return0 = $this->balance($newArray[0], $newArray[1]);
        $return1 = $this->balance($newArray[0], $newArray[2]);
        switch((string)$return0.(string)$return1) {
            case ‘11‘:
                $this->theSpecial = -1;
                return 0 + $this->compareThird($newArray[0]);
            case ‘10‘:
                $this->theSpecial = 1;
                return 3 + $this->compareThird($newArray[1]);
            case ‘01‘:
                $this->theSpecial = 1;
                return 6 + $this->compareThird($newArray[2]);
            case ‘00‘:
                return 9;
            case ‘0-1‘:
                $this->theSpecial = -1;
                return 6 + $this->compareThird($newArray[2]);
            case ‘-10‘:
                $this->theSpecial = -1;
                return 3 + $this->compareThird($newArray[1]);
            case ‘-1-1‘:
                $this->theSpecial = 1;
                return 0 + $this->compareThird($newArray[0]);
        }
    }

    /*
     * 通过前两次的比对，知道特别球是重还是轻，然后在三个球中比对一次，知道三个球中特殊球的索引
     */
    public function compareThird($childArray) {
        $return = $this->balance($childArray[0], $childArray[1]);
        switch($return) {
            case 1:
            case -1:
                if ($return == $this->theSpecial) {
                    return 1;
                } else {
                    return 0;
                }
                break;
            case 0:
                return 2;
                break;
        }
    }
}

echo ‘<pre>‘;
print_r($data);
$filter = new filterBall();
echo sprintf(‘键值：%s, 比对了%s次‘, $filter->execute($data), $filter->balanceTimes);