Problem

In a Meta mobile app such as Facebook or Instagram, UI debugging often requires inspecting the full view tree from a root view. Given the root of a view hierarchy, return a formatted list of strings representing the entire hierarchy in top-down order, with indentation showing parent-child relationships.

Each view has a name string and a list of children. Write a function that traverses the hierarchy and returns one string per view. The root should have no indentation, its children should be prefixed with two spaces, grandchildren with four spaces, and so on.

Formal Specification

• Input: root, a view node object or None
• View node fields:
  • name: string
  • children: list of child view nodes
• Output: a list of strings representing the hierarchy

Examples

Example 1

Input:
root = View("Root", [View("Header"), View("Body")])

Output:
["Root", "  Header", "  Body"]

Explanation: Header and Body are direct children of Root, so each is indented by two spaces.

Example 2

Input:
root = View("Root", [View("Feed", [View("StoryTray"), View("Composer")])])

Output:
["Root", "  Feed", "    StoryTray", "    Composer"]

Explanation: StoryTray and Composer are grandchildren of Root, so they use four spaces.

Constraints

• The number of views is in the range [0, 10^4]
• Each view name has length [1, 100]
• Each node may have 0 to 100 children
• The hierarchy is a tree with no cycles