Introduction - If you have any usage issues, please Google them yourself
A certain period, A B between army troops and a war breaks out. A military order to prevent easily find their headquarters, B Army planted a binary tree type of formation, so that both can communicate with each other, but also can be a good hiding spot headquarters. A total of n nodes, each with a numbered, headquartered in one of these nodes. Know the former military headquarters preorder in row B in the first m-bit string label. A military find data structures you have learned, you get the pre-order traversal B Army based on known preorder and postorder traversal, and draw B army headquarters on exactly how much the node labeled.