Question

I’ve got vector A which contains numbers 1,7,9,9,3,13,3
I’ve got vector B which contains numbers 9,11,7,7,3,2,1

I need to get vector C which will contain every element from two vectors below but only one time each (for example numbers 9 from vector A shouldn’t repeat)
so C should contain 1,7,9,3,13,11,2

This code will make vector C which will be union of two vectors but there will be some numbers repeating (if one vector includes 3x number 1 then C includes also 3x number 1)

vector<int>union(vector<int>A,vector<int>B)
{ 
    sort(A.begin(),A.end());
    sort(B.begin(),B.end());
    vector<int> C(A.size()*2);            //vector A has same size as vector B

    vector<int>::iterator it= set_union(A.begin(),A.end(),B.begin(),B.end(),C.begin());
    C.resize(it-C.begin());
    return C;
}

It has to be working as fast as possible.
What is the best way to do it so?

Answer 1

The right solution for this problem is to sort each vector first and then get intersection/union/filtering in a way that is similar to the sink sorting.