Writing an algorithm to decide whether a target number can be reached with a set of other numbers and specific operators?

Question

I\'m trying to learn more about algorithm design, and I\'ve set myself the challenge of creating a simple game that presents users with an array of numbers, a target number,

Answer 1

1. Enumerate all possible expressions. For numbers 1,2,3,and operator + and - ,you can get:1+2+3,1+2-3,1-2+3,1-2-3.

2. Evaluate all possible expressions.