PHP Two fork Tree (i): two fork search tree

On the principle of binary search tree on-line resources are quite many, and the situation is a little complicated, so here I will no longer state, directly on the code bar:

#bst. php Files <!--? php/** * Author:zhongjin * TIME:2016/10/20 11:53 * Description: Two fork Find tree *///node class node{public $key    ;    Public $parent;    Public $left;     Public $right;        Public function __construct ($key) {$this--->key = $key;        $this->parent = NULL;        $this->left = NULL;    $this->right = NULL;     }}//Two forks search tree class bst{public $root; /** * Initialize tree structure * @param an array of $arr initialization tree structure * @return NULL */Public function init ($arr) {$this-&gt        ; root = new Node ($arr [0]);        for ($i = 1; $i < count ($arr), $i + +) {$this->insert ($arr [$i]);     }}/** * (internal) middle order traversal * @param $root (tree or subtree) root node * @return NULL */Private Function Mid_order ($root)            {if ($root! = NULL) {$this->mid_order ($root->left); Echo $root->key.            " ";        $this->mid_order ($root->right);   }}/** * (external) middle order traversal * @param null * @return NULL  */Public Function Midorder () {$this->mid_order ($this->root);        }/** * Find the node in the tree for $key * @param $key number to search * @return $key corresponding node */function Search ($key) {        $current = $this->root;            while ($current! = NULL) {if ($current->key = = $key) {return $current;            } elseif ($current->key > $key) {$current = $current->left;            } else {$current = $current->right;    }} return $current;        /** * Find the Minimum keyword in the tree * @param $root root node * @return the node corresponding to the minimum keyword */function search_min ($root) {        $current = $root;        while ($current->left! = NULL) {$current = $current->left;    } return $current;        /** * Find the largest keyword in the tree * @param $root root node * @return The node for the maximum keyword */function Search_max ($root) {        $current = $root; while ($current->right! =NULL) {$current = $current->right;    } return $current; /** * Find the direct precursor node of a $key in the middle sequence traversal * @param $x node reference for the precursor node to be found * @return precursor node reference */function predecessor ($x {//Left dial hand node exists, directly returns the right child node of the left child node if ($x->left! = NULL) {return $this->search_max ($x->left        );        }//Otherwise finds its parent node until the current node is on the right side of the parent node $p = $x->parent;            If X is the left child of P, stating that P is the successor of X, we need to find that P is the precursor of x while ($p! = NULL && $x = = $p->left) {$x = $p;        $p = $p->parent;    } return $p;    /** * Find the direct successor of a $key in the middle sequence traversal * @param $x node Reference for the successor to be found * @return subsequent node reference */function successor ($x)        {if ($x->left! = NULL) {return $this->search_min ($x->right);        } $p = $x->parent;            while ($p! = NULL && $x = = $p->right) {$x = $p;        $p = $p->parent;    } return $p;    }/** * Insert $key into the tree * @param $key number of trees to be inserted * @return NULL */function Insert ($key) {if (!is_null ($this->search ($key)) {throw new Exception (' node '. $key. ' already exists, cannot be inserted!        ');        } $root = $this->root;        $inode = new Node ($key);        $current = $root;        $prenode = NULL;            Find the appropriate insertion position for $inode while ($current! = NULL) {$prenode = $current;            if ($current->key > $inode->key) {$current = $current->left;            } else {$current = $current->right;        }} $inode->parent = $prenode;        if $prenode = = NULL, the proof tree is an empty tree if ($prenode = = null) {$this->root = $inode;            } else {if ($inode->key < $prenode->key) {$prenode->left = $inode;            } else {$prenode->right = $inode;    }}//return $root; /** * Delete the $key corresponding node in the tree * @param $kEY number of nodes to delete * @return Null */function Delete ($key) {if (Is_null ($this->search ($key))) { throw new Exception (' node '. $key. "Does not exist, delete failed!"        ");        } $root = $this->root;        $dnode = $this->search ($key);        if ($dnode->left = = NULL | | $dnode->right = = null) {#如果待删除结点无子节点或只有一个子节点, then c = dnode $c = $dnode;        The else {#如果待删除结点有两个子节点, C is the direct successor of Dnode, and the value of the node to be deleted is subsequently replaced by the value of its successor $c = $this->successor ($dnode);        }//Regardless of the previous situation, to the last C only one side of the child node if ($c->left! = NULL) {$s = $c->left;        } else {$s = $c->right; if ($s! = NULL) {#将c的子节点的父母结点置为c的父母结点, here C can have only 1 child nodes, because C cannot be a direct successor to Dnode if C has two child nodes $s->paren        t = $c->parent; if ($c->parent = = NULL) {#如果c的父母为空, C=dnode is the root node, and the root node is immediately placed as a child node of the root node, where Dnode is the root node and has two child nodes.        C is the successor node of Dnode, C parents will not be empty, will not enter the IF $this->root = $s; } else if ($c == $c->parent->left) {#如果c是其父节点的左右子节点, the left and right child nodes of C parents are set to the left and right child nodes of c $c->parent->left = $s;        } else {$c->parent->right = $s;        } #如果c!=dnode, stating that C is the successor of Dnode, Exchange the key value of C and Dnode if ($c! = $dnode) {$dnode->key = $c->key;    } #返回根节点//return $root;        /** * (inward) Gets the depth of the tree * @param $root root node * @return Tree Depth */Private Function getdepth ($root) {        if ($root = = NULL) {return 0;        } $DL = $this->getdepth ($root->left);         $DR = $this->getdepth ($root->right);    Return ($dl > $dr? $DL: $DR) + 1; /** * (external) Gets the depth of the tree * @param null * @return NULL */Public Function Depth () {return $this    ->getdepth ($this->root); }}

debugging when you can call the sequence traversal to do, I in the previous blog provides PHP implementation of the two-tree graphics, with visual help can better help us to debug, detailed everyone can visit my previous blog: "Using PHP to achieve two-tree graphics display"

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