[数据结构与算法]二叉树最大深度，leetcode习题

二叉树最大深度

//1.迭代法
 public int maxdepth(Leetcode.TreeNode root){

        int depth = 0;
        if (root == null){
            return 0;
        }

        Deque<Leetcode.TreeNode> deque = new LinkedList<>();
        deque.offer(root);

        while(!deque.isEmpty()){

            int size = deque.size();
            depth++;

            //遍历辅助队列
            for (int i = 0;i<size;i++){

                Leetcode.TreeNode node = deque.poll();
                //将此节点的左右节点压入队列中
                if (node.left != null)deque.offer(node.left);
                if (node.right != null)deque.offer(node.right);

            }
        }
        return depth;
    }

//递归版
 public static int maxdepth2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int leftdepth = maxdepth2(root.left);
        int rightdepth = maxdepth2(root.right);
        return Math.max(leftdepth, rightdepth) + 1;

    }
思路：利用队列进行层序遍历，然后利用队列做辅助结构，对深度进行+1.