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。
复制代码代码如下:php ob_start();// Here we need to include the binary tree class Class Binary_Tree_Node() {// You can find the details at}ob_end_clean();// Define a class to implement self sorting binary tree class 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 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 $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, 90 echo '', implode(', ', $sort_as_you_go->returnsorted()), '';?>