Easy · Trees

N-ary tree traversal iteratively

Given the root of an n-ary tree (the tests list nodes as {val, children} with child indices, node 0 being the root), return its preorder traversal — each node's value before the values of its subtrees, children taken left to right — computed iteratively rather than recursively.

Examples

Example 1

{
  "nodes": [
    {"val": 1, "children": [1, 2, 3]},
    {"val": 2, "children": [4, 5]},
    {"val": 3, "children": []},
    {"val": 4, "children": []},
    {"val": 5, "children": []},
    {"val": 6, "children": []}
  ]
}

Output: [1, 2, 5, 6, 3, 4]

Example 2

{
  "nodes": [
    {"val": 10, "children": [1, 2]},
    {"val": 20, "children": [3]},
    {"val": 30, "children": []},
    {"val": 40, "children": [4, 5]},
    {"val": 50, "children": []},
    {"val": 60, "children": []}
  ]
}

Output: [10, 20, 40, 50, 60, 30]

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