good-output.txt - Android社区 - https://www.androidos.net.cn/

pre-order traversal, with recursion: 
35 28 20 25 23 26 30 60 70 65 64 68 

pre-order traversal, without recursion: 
35 28 20 25 23 26 30 60 70 65 64 68 

in-order traversal, with recursion: 
20 23 25 26 28 30 35 60 64 65 68 70 

in-order traversal, without recursion: 
20 23 25 26 28 30 35 60 64 65 68 70