All files / leetCode 0103.ts

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import type { TreeNode } from './Tree'
 
export default function zigzagLevelOrder(
  root: TreeNode<number> | null,
): number[][] {
  const res: number[][] = []
 
  if (root === null)
    return res
 
  const queue = [root]
  let zigzag = true
 
  while (queue.length > 0) {
    const len = queue.length
    const row: number[] = []
 
    for (let i = 0; i < len; i++) {
      const node = queue.shift() as TreeNode<number>
 
      if (zigzag)
        row.push(node.val)
      else
        row.unshift(node.val)
 
      if (node.left !== null)
        queue.push(node.left)
      if (node.right !== null)
        queue.push(node.right)
    }
 
    zigzag = !zigzag
    res.push(row)
  }
 
  return res
}