59. 螺旋矩阵 II

<?php
class Solution {
    public function generateMatrix($n) {
        if ($n <= 0) {
            return [];
        }
        $forwards = ['R', 'D', 'L', 'U'];
        $forward = 'R';
        $minI = $minJ = 0;
        $maxI = $maxJ = $n - 1;
        $num = 1;
        $ret = [];
        while($num <= pow($n, 2)) {
            if ($forward == 'R') {
                for ($j = $minJ; $j <= $maxJ; $j++) {
                    $ret[$minI][$j] = $num++;
                }
                $minI++;
            } elseif ($forward == 'D') {
                for ($i = $minI; $i <= $maxI; $i++) {
                    $ret[$i][$maxJ] = $num++;
                }
                $maxJ--;
            } elseif ($forward == 'L') {
                for ($j = $maxJ; $j >= $minJ; $j--) {
                    $ret[$maxI][$j] = $num++;
                }
                $maxI--;
            } else {
                for ($i = $maxI; $i >= $minI; $i--) {
                    $ret[$i][$minJ] = $num++;
                }
                $minJ++;
            }
            // 修改方向
            $forward = $forwards[(array_search($forward, $forwards) + 1) % 4];
        }
        return $ret;
    }
}
$n = 5;
$cls = new Solution();
$r = $cls->generateMatrix($n);
array_walk($r, function (&$v) {
    ksort($v);
    $v = implode(',', $v);
});
print_r($r);