What is the order in which nodes of this tree are visited in depth-first order?
go check the website for the picture, #46
A: Z, =, Y, *, A, +, X
B: =, Z, +, *, X, Y, A
C: Y, A, *, X, Z, +, =
D: =, Z, +, *, Y, A, X
E: Z, Y, A, *, X, +, =
In depth-first order, a node is visited and then its children are visited in order (same as preorder).