Twenty Four, Again

there are only 4! permutations of the numbers.

There are only 4^3 combinations of operators.

There are only 10 combinations of parenthesis.

• (xx)xx
• x(xx)x
• xx(xx)
• (xxx)x
• ((xx)x)x
• (x(xx))x
• x(xxx)
• x((xx)x)
• x(x(xx))
• (xx)(xx)

4! * 4^3*10 = 15360

Just iterate through all of them and find the cheapest.

One of the challenges to this problem SHOULD be to actually evaluate the expression...they want you to use a recursive descent parser (which you SHOULD know how to build....), but you can just dump it in java's javascript engine and call "evaluate" which will evaluate the string-based expression for you.