Subset question didnt get it

I didn’t get the subset one. It was a little bit confusing can I get the concept with one example. I tried to solve the codechef question but i failed.

if you want subset of 3 numbers , you iterate from 1 to pow(2,n)
now ex n=3;
001
010
011
100
101
110
111
now at the binary number differs at least at one place,
so , now at all places where we have “1” , we will count that index in the subset.
for ex say 5=“101”
now we have 1 at 0 place and 2nd place, so they will be included in the subset

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