LeetCode104-二叉树的最大深度

LeetCode104-二叉树的最大深度

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public int maxDepth(TreeNode root) {
       if (root == null) return 0;
       Queue<TreeNode> queue = new LinkedList<>();
       int deep = 1;
       queue.offer(root);
       int levelSize = 1;
       while (!queue.isEmpty()) {
           TreeNode poll = queue.poll();
           levelSize--;
           if (poll.left != null) {
               queue.offer(poll.left);
           }
           if (poll.right != null) {
               queue.offer(poll.right);
           }
           if (levelSize==0){
               levelSize = queue.size();
               deep++;
           }
       }
       return deep;
   }