Leetcode PHP题解--D125 107. Binary Tree Level Order Traversal II

val = $value; } * } */ class Solution { private $vals = []; /** * @param TreeNode $root * @return Integer[][] */ function levelOrderBottom($root) { $this->preOrder($root, 0); return array_reverse($this->vals); } function preOrder($node, $level){ if(is_null($node)){ return; } if(!isset($this->vals[$level])){ $this->vals[$level] = []; } $this->vals[$level][] = $node->val; if($node->left){ $this->preOrder($node->left, $level+1); } if($node->right){ $this->preOrder($node->right, $level+1); } } }