Sum it up(Rec and backtracking)

#1

give me some hint about this question?

#2

Read about sets and vectors and the use set<vector>
.
Then use simple idea that 2 recursive calls are to be made and in one call i might include the element in the sum and in other call i will not include the element . As soon as i reach the last index i will check if the sum is 0 then i will add that collection that i have made so far into my total collection.