如何实现二叉搜索树节点最小距离

/** * Definition for a binary tree node. * type TreeNode struct { *     Val int *     Left *TreeNode *     Right *TreeNode * } */func minDiffInBST(root *TreeNode) int {    _,diff:=bst(root,-100001,100001)    return diff}
func bst(root*TreeNode,pre,diff int)(int,int){    if root==nil{        return pre,diff    }    pre,diff=bst(root.Left,pre,diff)    if root.Val-pre          diff=root.Val-pre    }    pre=root.Val      pre,diff=bst(root.Right,pre,diff)    return pre,diff}

/** * Definition for a binary tree node. * type TreeNode struct { *     Val int *     Left *TreeNode *     Right *TreeNode * } */  var a[]intfunc minDiffInBST(root *TreeNode) int {    a=nil    visit(root)    min:=100    for i:=0;i        if min>a[i+1]-a[i]{            min=a[i+1]-a[i]        }    }    return min}
func visit(root *TreeNode){    if root==nil{        return    }    visit(root.Left)    a=append(a,root.Val)    visit(root.Right)}