[PHP知识库]螺旋矩阵【php版】

思路:模拟遍历的过程,每次访问的正好是按螺旋顺序应该访问的元素，共访问 m* n次

	function spiralOrder($matrix) {
		$rows = count($matrix);
		$cols = count($matrix[0]);
		if ($rows == 0 || $cols == 0) {
			return [];
		}
		$count = $rows * $cols;
		$visited = array_fill(0, $rows*$cols, false);
		$direction = [
				[0, 1],
				[1, 0],
				[0, -1],
				[-1, 0],
			];
		$dirIndex = 0;
		$r = 0;
		$c = 0;
		$_R = [];
		while ($count-- > 0) {
			$index = $r * $cols + $c;
			$visited[$index] = true;
			$_R[] = $matrix[$r][$c];

			$r_new = $r + $direction[$dirIndex][0];
			$c_new = $c + $direction[$dirIndex][1];
			if ($r_new > $rows - 1 || $r_new < 0 || $c_new > $cols - 1 || $c_new < 0 || $visited[$r_new*$cols+$c_new]) {
				$dirIndex = ($dirIndex + 1) % 4;
			}
			$r = $r + $direction[$dirIndex][0];
			$c = $c + $direction[$dirIndex][1];
		}
		return $_R;
	}