Research Engineer-Heterogeneous computing (ML)50min OA
invert a binary tree to double-linked list in place
文件读取关于binary tree的相关信息，转换为double-linked list in place，输出string。
eg
text.in:
node id left child right child
5 -1 -1
2 1 5
1 -1 -1
output:
1 2 5