(C++) std::set_intersection

 

std::set_intersection is an STL algorithm to create the intersection set of two sets (stored in any type of container).

 

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#include <algorithm> #include <cassert> #include <iostream> #include <iterator> #include <vector> int main() {   //v contains all values from zero to ten   std::vector<int> v;   v.push_back(0);   v.push_back(1);   v.push_back(2);   v.push_back(3);   v.push_back(4);   v.push_back(5);   v.push_back(6);   v.push_back(7);   v.push_back(8);   v.push_back(9);   //w contains all squares from 1 to an including 25   std::vector<int> w;   w.push_back( 1);   w.push_back( 4);   w.push_back( 9);   w.push_back(16);   w.push_back(25);   //x is the intersection of v and w   std::vector<int> x;   std::set_intersection(v.begin(),v.end(),w.begin(),w.end(),     std::back_inserter(x));   //so x contains all three squares between zero to ten   assert(x.size() == 3);   assert(x[0] == 1);   assert(x[1] == 4);   assert(x[2] == 9);   //Show x on screen   std::copy(x.begin(),x.end(),std::ostream_iterator<int>(std::cout," "));   std::cout << '\n'; }

 

Screen output:

 

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1 4 9