Algorithm http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=0033

Ball.php

<?php
class Ball
{
    public $dataSets = array();

    public function run($input)
    {
        $this->set($input);
        $results = array();
        foreach ($this->dataSets as $d) {
            $results[] = $this->parse(explode(' ', $d));
        }
        return implode("\n", $results);
    }

    public function set($input)
    {
        $splited = preg_split('/[\r\n|\r|\n]/', $input);
        for ($i = 0; $i < count($splited); $i++) {
            if ($i === 0) continue;
            $this->dataSets[] = $splited[$i];
        }
    }

    public function parse(Array $data, $b = null, $c = null)
    {
        if ($b === null && $c === null) list($b, $c) = array(new AckArray(), new AckArray());
        if (empty($data)) return 'YES';

        $input_num = array_shift($data);
        if ($b->last() >= $input_num and $c->last() >= $input_num) return 'NO';

        if ($b->last() >= $input_num) {
            $c->add($input_num);
            return $this->parse($data, $b, $c);
        }
        if ($c->last() >= $input_num) {
            $b->add($input_num);
            return $this->parse($data, $b, $c);
        }

        ($b->last() > $c->last()) ? $b->add($input_num) : $c->add($input_num);
        return $this->parse($data, $b, $c);
    }
}

class AckArray extends ArrayObject
{
    public function first()
    {
        if ($this->count() === 0) return null;
        return $this->offsetGet(0);
    }

    public function last()
    {
        if ($this->count() === 0) return null;
        return $this->offsetGet($this->last_index());
    }

    public function add($value)
    {
        $this->offsetSet($this->last_index() + 1, $value);
    }

    public function last_index()
    {
        return $this->count() - 1;
    }
}

BallTest.php

<?php
require_once 'Ball.php';
class BallTest extends PHPUnit_Framework_TestCase
{
    public function setUp()
    {
        $this->ball = new Ball();
        $this->input = <<< __EOS__
2
3 1 4 2 5 6 7 8 9 10
10 9 8 7 6 5 4 3 2 1
__EOS__;
    }

    /**
     * @test
     */
    public function should_have_two_dataSet()
    {
        $this->ball->run($this->input);
        $this->assertEquals(2, count($this->ball->dataSets));
    }

    /**
     * @test
     */
    public function parse_should_return_YES_if_input_is_valid()
    {
        $input = '3 1 4 2 5 6 7 8 9 10';
        $expect = 'YES';
        $this->assertEquals($expect, $this->ball->parse(explode(' ', $input)));
    }

    /**
     * @test
     */
    public function parse_should_return_NO_if_input_is_invalid()
    {
        $input = '10 9 8 7 6 5 4 3 2 1';
        $expect = 'NO';
        $this->assertEquals($expect, $this->ball->parse(explode(' ', $input)));
    }

    /**
     * @test
     */
    public function run_should_return_result_rows()
    {
        $expect = <<< __EOS__
YES
NO
__EOS__;
        $this->assertEquals($expect, $this->ball->run($this->input));
    }
}

main.php

<?php
$ball = new Ball();
$input = <<< __EOS__
2
3 1 4 2 5 6 7 8 9 10
10 9 8 7 6 5 4 3 2 1
__EOS__;

echo $ball->run($input);
/*
YES
NO
*/