OJ Board

OK, you are rigth about the unary operations. Here are some more test cases and the output my AC program gives.


a + b
b - z
a+b--+c++
c+f--+--a
f-- + c-- + d-++e

a--+b--+c--+d--+e--+f--+g--+h--+i++-j++-k++-l++-m++-n++-o++-p++-q++-r++-s+t-u+v
--z+a--
a
z
++ x+--y+z++
a++-c++-m+ + +o+k ...

Have you considered the following cases?

-a
+a

Anyway, test cases like a+b-a won't be in the input.

A good thing to do is to determine the absolute maximum value of the answer before doing the DFS, and then quit searching if the maxvalue has been found. Helps a lot with a simple 0.144 grid.

Although not mentioned in the problem description, the problem input is in the multiple input format as indicated by the green submit icon in the contents list.
If your program knows this and still gets WA, your problem is somewhere else.