如果给定的树可以是任意的二叉树呢?你之前的给出的算法还有效吗?
注意：你只能使用常量的额外内存空间
例如：
给出的二叉树如下： 1↵ / ↵ 2 3↵ / ↵ 4 5 7
调用完你给出的函数之后，这棵树应该变成：
1 -> NULL↵ / ↵ 2 -> 3 -> NULL↵ / ↵ 4-> 5 -> 7 -> NULL
<?php class TreeLinkNode { public $left = null; public $right = null; public $next = null; public $val; public function __construct($val) { $this->val = $val; } } function connect($root) { if ($root->left != null && $root->right != null) { $root->left->next = $root->right; } if ($root->next != null) { if ($root->next->left != null) { if ($root->right != null) { $root->right->next = $root->next->left; } elseif ($root->left != null) { $root->left->next = $root->next->left; } } if ($root->next->right != null) { if ($root->right != null) { $root->right->next = $root->next->right; } elseif ($root->left != null) { $root->left->next = $root->next->right; } } } if ($root->left != null) { connect($root->left); } if ($root->right != null) { connect($root->right); } return $root; } $node1 = new TreeLinkNode(1); $node2 = new TreeLinkNode(2); $node3 = new TreeLinkNode(3); $node4 = new TreeLinkNode(4); $node5 = new TreeLinkNode(5); $node6 = new TreeLinkNode(6); $node7 = new TreeLinkNode(7); $node1->left = $node2; $node1->right = $node3; $node2->left = $node4; $node2->right = $node5; //$node3->left = $node6; $node3->right = $node7; $root = connect($node1); output($root); function output($root) { if ($root != null) { print $root->val.'->'.$root->next->val.';'; } if ($root->left != null) { output($root->left); } if ($root->right != null) { output($root->right); } }