/**
 *
 * Ashish Patel
 * e: ashishsushilPatel@gmail.com
 * w: https://ashish.me
 *
 */

function TreeNode(val) {
  this.val = val
  this.left = this.right = null
}

const binaryTreeZigzagLevelOrderTraversal = root => {
  if (!root) {
    return []
  }
  let result = []
  let queue = [root]
  let even = true
  while (queue.length !== 0) {
    let size = queue.length
    let tempQueue = []
    for (let i = 0; i < size; i++) {
      const element = queue.shift()
      if (element) {
        if (even) {
          tempQueue.push(element.val)
        } else {
          tempQueue.unshift(element.val)
        }
      }
      if (element && element.left) {
        queue.push(element.left)
      }
      if (element && element.right) {
        queue.push(element.right)
      }
    }
    even = !even
    result.push(tempQueue)
  }
  return result
}

test('binaryTreeZigzagLevelOrderTraversal', () => {
  const t1 = new TreeNode(3)
  t1.left = new TreeNode(9)
  t1.right = new TreeNode(20)
  t1.right.left = new TreeNode(15)
  t1.right.right = new TreeNode(7)
  expect(binaryTreeZigzagLevelOrderTraversal(t1)).toEqual([[3], [20, 9], [15, 7]])
})