For the number being processed, find the two closest numbers to the element on the left and right sides that are larger than it, and take the smaller number as the root node of the current number
The process of building a tree is implemented with 2 tables, a left table and a right table
for example
3 4 5 1 2
right table
key value
3 4
4 5
5 null
1 2
2 null
The establishment of the table uses the stack structure, keeping the elements in the stack at the bottom and the decimal at the top
Press in 3
Push 4 Pop 3 Record 3 4
Push 5 Pop 4 Record 4 5
Press in 1 does not bounce
Push 2 Pop 1 Record 1 2
-------- pop 2 records 2 null
-------- pop 5 records 5 null