flatten-binary-tree-to-linked-list.go

// https://leetcode.com/problems/flatten-binary-tree-to-linked-list
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func flatten(root *TreeNode)  {
    stack := []*TreeNode{}
    
    for root != nil {
        if root.Right != nil {
            stack = append(stack, root.Right)
        }
        
        if root.Left != nil {
            stack = append(stack, root.Left)
        }
        
        root.Left = nil
        
        if len(stack) > 0 {
            top := stack[len(stack) - 1]
            stack = stack[:len(stack) - 1]
            
            root.Right = top
            root = top
        } else {
            root = nil
        }
    }
}