/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func flatten(root *TreeNode) {
list:=preTravel(root)
for i:=1;i<len(list);i++{
pre,node:=list[i-1],list[i]
pre.Right=node
pre.Left=nil
}
}
func preTravel(root *TreeNode)[]*TreeNode{
list:=[]*TreeNode{}
if root!=nil{
list=append(list,root)
list=append(list,preTravel(root.Left)...)
list=append(list,preTravel(root.Right)...)
}
return list
}