PHP Class&Object -- PHP 自排序二叉树

在节点之间再应用一些排序逻辑，二叉树就能提供出色的组织方式。对于每个节点，都让满足所有特定条件的元素都位于左节点及其子节点。在插入新元素时，我们需要从树的第一个节 点(根节点)开始，判断它属于哪一侧的节点，然后沿着这一侧找到恰当的位置，类似地，在读取数据时，只需要使用按序遍历方法来遍历二叉树。

 <?phpob_start();// Here we need to include the binary tree classClass Binary_Tree_Node() { // You can find the details at //http://blog.csdn.net/dengzonghuan/archive/2009/03/17/3999372.aspx}ob_end_clean();// Define a class to implement self sorting binary treeclass Sorting_Tree { // Define the variable to hold our tree: public $tree; // We need a method that will allow for inserts that automatically place // themselves in the proper order in the tree public function insert($val) { // Handle the first case: if (!(isset($this->tree))) { $this->tree = new Binary_Tree_Node($val); } else { // In all other cases: // Start a pointer that looks at the current tree top: $pointer = $this->tree; // Iteratively search the tree for the right place: for(;;) { // If this value is less than, or equal to the current data: if ($val <= $pointer->data) { // We are looking to the left ... If the child exists: if ($pointer->left) { // Traverse deeper: $pointer = $pointer->left; } else { // Found the new spot: insert the new element here: $pointer->left = new Binary_Tree_Node($val); break; } } else { // We are looking to the right ... If the child exists: if ($pointer->right) { // Traverse deeper: $pointer = $pointer->right; } else { // Found the new spot: insert the new element here: $pointer->right = new Binary_Tree_Node($val); break; } } } } } // Now create a method to return the sorted values of this tree. // All it entails is using the in-order traversal, which will now // give us the proper sorted order. public function returnSorted() { return $this->tree->traverseInorder(); }}// Declare a new sorting tree:$sort_as_you_go = new Sorting_Tree();// Let's randomly create 20 numbers, inserting them as we go:for ($i = 0; $i < 20; $i++) { $sort_as_you_go->insert(rand(1,100));}// Now echo the tree out, using in-order traversal, and it will be sorted:// Example: 1, 2, 11, 18, 22, 26, 32, 32, 34, 43, 46, 47, 47, 53, 60, 71,// 75, 84, 86, 90echo '<p>', implode(', ', $sort_as_you_go->returnSorted()), '</p>';?>