PHP realizes printing binary tree from top to bottom code sharing

This time I will share with you the code for PHP to print a binary tree from top to bottom. What are the precautions for PHP to print a binary tree from top to bottom? Here are the actual cases, let's take a look.

Question

Print each node of the binary tree from top to bottom, and print nodes at the same level from left to right.

Solution

Each layer of trees is printed from left to right, so the left and right subtrees of the node need to be stored, because first in, first out , so use

queue.

Implementation code

/*class TreeNode{
  var $val;
  var $left = NULL;
  var $right = NULL;
  function construct($val){
    $this->val = $val;
  }
}*/
function PrintFromTopToBottom($root)
{
  $queueVal = array();
  $queueNode = array();
  if($root == NULL)
    return $queueVal;
  array_push($queueNode, $root);
  while(!empty($queueNode)){
    $node = array_shift($queueNode);
    if($node->left != NULL)
      array_push($queueNode,$node->left);
    if($node->right != NULL)
      array_push($queueNode,$node->right);
    array_push($queueVal,$node->val);
  }
  return $queueVal;
}

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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