题解 | #二叉搜索树与双向链表#

package main

import . "nc_tools"

/*
 * type TreeNode struct {
 *   Val int
 *   Left *TreeNode
 *   Right *TreeNode
 * }
 */

/**
 *
 * @param pRootOfTree TreeNode类
 * @return TreeNode类
 */
func Convert(pRootOfTree *TreeNode) *TreeNode {
	// write code here
	if pRootOfTree == nil {
		return nil
	}

	var head, pre *TreeNode
	var dfs func(pRootOfTree *TreeNode)
	dfs = func(pRootOfTree *TreeNode) {
		if pRootOfTree == nil {
			return
		}
		dfs(pRootOfTree.Left)
		if pre == nil {
			head = pRootOfTree
			pre = pRootOfTree
		} else {
			pRootOfTree.Left = pre
			pre.Right = pRootOfTree
			pre = pRootOfTree
		}
		dfs(pRootOfTree.Right)
	}
	dfs(pRootOfTree)

	return head
}