Algorithm

There's a n-element array of integers- 1 or 2.
We have to find subsequence which sum equals x.
How to do that ? I have no fucking idea.
Inb4 bruteforce

Start with two indices, i and j, and an integer N representing the sum of all numbers between A[i] and a[j], inclusively.
1) Increment j, add A[j] to N.
2) If N = x, you're done. If N < x, back to the imageboardsstep 1.
3) Subtract A[i] from N. Increment i. Go to 2.