D96 530. Minimum Absolute Difference in BST

题目链接

530. Minimum Absolute Difference in BST

题目分析

给定一个二叉树，返回任意两节点的最小差。

思路

先获取所有节点值，再逐个比对。不过这样效率很低。

最终代码

<?php
/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     public $val = null;
 *     public $left = null;
 *     public $right = null;
 *     function __construct($value) {$this->val = $value;}
 * }
 */
class Solution {protected $values = [];
    
        /**
             * @param TreeNode $root
                  * @return Integer
                       */
                           function getMinimumDifference($root) {$this->preOrder($root);
                                           $amount = count($this->values);
                                                   $minValue = 9999999;
                                                           for($i=0; $i<$amount; $i++){for($j=$i+1;$j<$amount; $j++){$diff = abs($this->values[$i] - $this->values[$j]);
                                                                                                       if($diff<$minValue){$minValue = $diff;}
                                                                                                                                                       }
                                                                                                                                                               }
                                                                                                                                                                       return $minValue;
                                                                                                                                                                           }
                                                                                                                                                                               
                                                                                                                                                                                   function preOrder($root){if(is_null($root->val)){return;}
                                                                                                                                                                                                                      $this->values[] = $root->val;
                                                                                                                                                                                                                              if($root->left){$this->preOrder($root->left);
                                                                                                                                                                                                                                                  }
                                                                                                                                                                                                                                                          if($root->right){$this->preOrder($root->right);
                                                                                                                                                                                                                                                                              }
                                                                                                                                                                                                                                                                                  }
                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                      }

                                                                                                                                                                                                                                                                                  
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