Given a binary tree root, a ZigZag path for a binary tree is defined as follow:
<li>Choose <strong>any </strong>node in the binary tree and a direction (right or left).</li>
<li>If the current direction is right then move to the right child of the current node otherwise move to the left child.</li>
<li>Change the direction from right to left or right to left.</li>
<li>Repeat the second and third step until you can't move in the tree.</li>
Zigzag length is defined as the number of nodes visited - 1. (A single node has a length of 0).
Return the longest ZigZag path contained in that tree.
Example 1:
Input: root = [1,null,1,1,1,null,null,1,1,null,1,null,null,null,1,null,1] Output: 3 Explanation: Longest ZigZag path in blue nodes (right -> left -> right).
Example 2:
Input: root = [1,1,1,null,1,null,null,1,1,null,1] Output: 4 Explanation: Longest ZigZag path in blue nodes (left -> right -> left -> right).
Example 3:
Input: root = [1] Output: 0
Constraints:
<li>Each tree has at most <code>50000</code> nodes..</li>
<li>Each node's value is between <code>[1, 100]</code>.</li>