inorder for binary tree

例句：

1. 1.The team worked in order to finish theproject on time.
   团队按顺序工作以按时完成项目。
2. 2. She arranged her books inorder of importance.
   她根据重要性将书排列好。
3. 3. The teacher instructed the students tofollow the rules in order to avoid accidents.
   老师指示学生按照规则行事以避免事故。