D97 783. Minimum Distance Between BST Nodes

题目链接

783. Minimum Distance Between BST Nodes

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 {
    /**
     * @param TreeNode $root
     * @return Integer
     */
    function minDiffInBST($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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