/*
 * function TreeNode(x) {
 *   this.val = x;
 *   this.left = null;
 *   this.right = null;
 * }
 */
/**
 * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
 *
 *
 * @param root TreeNode类
 * @return int整型
 */
function maxDepth(root) {
    let res = 0;
    if (!root) return res;

    const queue = [root];

    while (queue.length) {
        res++;
        let size = queue.length;

        while (size-- > 0) {
            const node = queue.shift();
            node.left && queue.push(node.left);
            node.right && queue.push(node.right);
        }
    }

    return res;
}
module.exports = {
    maxDepth: maxDepth,
};