stl - What values are inserted in the set with this C++ code? -

i given interview question had following code. unfortunately, didn't right. explain code doing, commented line?

here code.

#include <iostream> #include <set>  struct c {     bool operator()(const int &a, const int &b) const     {         return % 10 < b % 10;     } };  int main() {     std::set<int> x({ 4, 2, 7, 11, 12, 14, 17, 2 });     std::cout << x.size();     std::set<int, c> y(x.begin(), x.end());  // not sure inserted in set     std::cout << y.size() << std::endl;      return 0; } 

when run, x contains in order:

2 4 7 11 12 14 17 

y contains in order:

11 2 4 7 

my hunch set reverses operator check equality (since set contains unique values). unique values of a%10 exist.