。 N 叉樹郵購遍歷

<?php
//Definition for a Node.
class Node {
    public $val = null;
    public $children = [];

    public function __construct($val) {
        $this->val = $val;
    }
}

/**
 * @param Node $root
 * @return integer[]
 */
function postorder($root) {
    ...
    ...
    ...
    /**
     * go to ./solution.php
     */
}

// Example 1:
$root1 = new Node(1);
$root1->children = [
    $node3 = new Node(3),
    new Node(2),
    new Node(4)
];
$node3->children = [
    new Node(5),
    new Node(6)
];

print_r(postorder($root1)); // Output: [5, 6, 3, 2, 4, 1]

// Example 2:
$root2 = new Node(1);
$root2->children = [
    new Node(2),
    $node3 = new Node(3),
    $node4 = new Node(4),
    $node5 = new Node(5)
];
$node3->children = [
    $node6 = new Node(6),
    $node7 = new Node(7)
];
$node4->children = [
    $node8 = new Node(8)
];
$node5->children = [
    $node9 = new Node(9),
    $node10 = new Node(10)
];
$node7->children = [
    new Node(11)
];
$node8->children = [
    new Node(12)
];
$node9->children = [
    new Node(13)
];
$node11 = $node7->children[0];
$node11->children = [
    new Node(14)
];

print_r(postorder($root2)); // Output: [2, 6, 14, 11, 7, 3, 12, 8, 4, 13, 9, 10, 5, 1]
?>