https://leetcode.com/problems/different-ways-to-add-parentheses/

Calculate all results of a function given a string.
For example input: "1+2-3*4"
it could compute as (((1+2)-3)*4) or ((1+2) -(3 * 4)) or (1+(2-3) * 4)
so the output is [0, -3, -9]