leetcode-103 二叉树的锯齿形层序遍历

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[][]}
 */
var zigzagLevelOrder = function (root) {
  let queue = [root],
    result = [];
  let count = 1;
  while (queue.length) {
    const newQueue = [],
      values = [];
    while (queue.length) {
      const node = queue.pop();
      if (node && count % 2 === 1) {
        values.push(node.val);
      }
      if (node && count % 2 === 0) {
        values.unshift(node.val);
      }
      if (node) {
        // 从左往右
        newQueue.unshift(node.left);
        newQueue.unshift(node.right);
      }
    }
    count++;
    queue = newQueue;
    if (values.length) {
      result.push(values);
    }
  }
  return result;
};