Level order (zigzag)

#1

10 true 20 true 40 false false true 50 false false true 30 true 60 false false true 73 false false

How to visualise a tree considering this input is in preorder ?

#2

IMG-20200708-WA0003
IMG-20200708-WA0003648×1152 36.5 KB

code for reference (only input)

(dry run for more understanding)