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