tree.ts

type TreeNode = [value: number, left: TreeNode | null, right: TreeNode | null]

const node: TreeNode =
  [1,
    [2,
      [4, null, null],
      null],
    [3,
      [5, null, null],
      [6, null, null]]]

function logTree(nodes: TreeNode[]) {
  if (nodes.length == 0) {
    return
  }

  const nextNodes: TreeNode[] = []

  for (const node of nodes) {
    process.stdout.write(`${node[0]} `);
    if (node[1]) nextNodes.push(node[1])
    if (node[2]) nextNodes.push(node[2])
  }

  process.stdout.write('\n')

  logTree(nextNodes)
}

logTree([node]);

function logTreeNoRecursion(nodes: TreeNode[]) {
  let queue = [...nodes]

  while (queue.length > 0) {
    let nextQueue: TreeNode[] = []

    for (const node of queue) {
      process.stdout.write(`${node[0]} `)
      if (node[1]) nextQueue.push(node[1])
      if (node[2]) nextQueue.push(node[2])
    }

    process.stdout.write('\n')

    queue = nextQueue
  }
}

logTreeNoRecursion([node])