BM28 二叉树的最大深度

/*
 * function TreeNode(x) {
 *   this.val = x;
 *   this.left = null;
 *   this.right = null;
 * }
 */

/**
  * 
  * @param root TreeNode类 
  * @return int整型
  */
function maxDepth( root ) {
    // write code here
        function getDepth(node){
        if(node === null){
           return 0
        }
        let leftDepth = getDepth(node.left)
        let rightDepth = getDepth(node.right)
        let depth = 1 + Math.max(leftDepth,rightDepth)
        return depth
    }
    return getDepth(root)
}
module.exports = {
    maxDepth : maxDepth
};