zigzagLevelOrder = (root) => {
    const isEdgeBase = (root === null);
    if (isEdgeBase) return [];
    
    return search(root);/* Time O(N) | Space O(N) */
}
BFS
Time O(N) | Space O(N)
https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
@param {TreeNode} root
@return {number[][]}