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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */

class Solution {
    class Node {
        TreeNode cur;
        int curCol;

        public Node (TreeNode cur, int curCol) {
            this.cur = cur;
            this.curCol = curCol;
        }
    }
    public int widthOfBinaryTree(TreeNode root) {
        if (root == null) return 0;
        int res = 1;
        Queue<Node> q = new LinkedList<>();
        q.offer(new Node(root, 0));
        while (!q.isEmpty()) {
            int curSize = q.size();
            int min = Integer.MAX_VALUE, max = Integer.MIN_VALUE;
            for (int i = 0; i < curSize; i++) {
                Node curNode = q.poll();
                TreeNode cur = curNode.cur;
                int curCol = curNode.curCol;
                min = Math.min(min, curCol);
                max = Math.max(max, curCol);
                if (cur.left != null) {
                    q.offer(new Node(cur.left, curCol * 2 + 1));
                } 
                if (cur.right != null) {
                    q.offer(new Node(cur.right, curCol * 2 + 2));
                }
            }
            res = Math.max(res, max - min + 1);
        }
        return res;
    }
}