783. Minimum Distance Between BST Nodes

题目

Given the root of a Binary Search Tree (BST), return the minimum difference between the values of any two different nodes in the tree.

Note: This question is the same as 530: https://leetcode.com/problems/minimum-absolute-difference-in-bst/

Example 1:

Input: root = [4,2,6,1,3]
Output: 1

Example 2:

Input: root = [1,0,48,null,null,12,49]
Output: 1

Constraints:

• The number of nodes in the tree is in the range [2, 100].
• 0 <= Node.val <= 10^5

题目大意

给你一个二叉搜索树的根节点 root ，返回 树中任意两不同节点值之间的最小差值 。

解题思路

• 本题和第 530 题完全相同。解题思路见第 530 题。

代码

package leetcode

import (
	"math"

	"github.com/halfrost/leetcode-go/structures"
)

// TreeNode define
type TreeNode = structures.TreeNode

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */

func minDiffInBST(root *TreeNode) int {
	res, nodes := math.MaxInt16, -1
	dfsBST(root, &res, &nodes)
	return res
}

func dfsBST(root *TreeNode, res, pre *int) {
	if root == nil {
		return
	}
	dfsBST(root.Left, res, pre)
	if *pre != -1 {
		*res = min(*res, abs(root.Val-*pre))
	}
	*pre = root.Val
	dfsBST(root.Right, res, pre)
}

func min(a, b int) int {
	if a > b {
		return b
	}
	return a
}

func abs(a int) int {
	if a > 0 {
		return a
	}
	return -a
}

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