Sum it Up Backtracking problem

#1


I am not able to use SET data structure please edit my code,I dont know how to store in SET.

#2

you use set correctly.
in your input there are two 1’s so when you find a subsequence 1 1 6 whose sum is 8 you insert it into set but set has a property that it insert only unique values so 1 will insert only one time.