minimum-distance-between-bst-nodes.go

package problem0783

import (
	"github.com/aQuaYi/LeetCode-in-Go/kit"
)

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

type TreeNode = kit.TreeNode

func minDiffInBST(root *TreeNode) int {
	res := 1<<63 - 1
	pre := 1>>63
	null := pre 

	var helper func(*TreeNode)
	helper = func (root *TreeNode) {
		if root.Left != nil {
			helper(root.Left)
		}
	
		if pre != null{
			res = min(res, root.Val-pre)
		}
	
		pre = root.Val
	
		if root.Right != nil {
			helper(root.Right)
		}
	}

	helper(root)

	return res
}



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