PHP implementation method of constructing two-fork tree algorithm

This article mainly introduces PHP implementation of the construction of two-fork tree algorithm, interested in the reference of friends, I hope to be helpful to everyone.

The tree is still important in the data structure, which means that the binary tree is represented by parentheses. Write a binary tree node class first:

Binary tree node class Btnode {public  $data;  Public $lchild = NULL;  Public $rchild = NULL;  Public function __construct ($data) {    $this->data = $data;  }}

Then construct a two-fork tree:

Function Createbtnode (& $root, String $str) {  $STRARR = Str_split ($STR);  $stack = [];  $p = NULL; Pointer  $top =-1;  $k = $j = 0;  $root = NULL;  foreach ($strArr as $ch) {    switch ($ch) {case      ' (':        $top + +;        Array_push ($stack, $p);        $k = 1;        break;      Case ') ':        array_pop ($stack);        break;      Case ', ':        $k = 2;        break;      Default:        $p = new Btnode ($ch);        if ($root = = NULL) {          $root = $p;        } else {          switch ($k) {case            1:              End ($stack)->lchild = $p;              break;            Case 2:              end ($stack)->rchild = $p;              break;          }        }        Break;}}}  

Here is a function to print a binary tree (middle sequence traversal):

function Printbtnode ($node) {  if ($node! = NULL) {    printbtnode ($node->lchild);    echo $node->data;    Printbtnode ($node->rchild);}  }

Operation Result:

Enter a string
"A (B (c,d), G (F))"