molecules.cpp: In function 'std::vector<long long int> find_subset(long long int, long long int, std::vector<long long int>)':
molecules.cpp:18:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
18 | for(int i=0;i<a.size();i++) b.insert(mp(a[i],i)) ;
| ~^~~~~~~~~
/tmp/cclPVXST.o: In function `main':
grader.cpp:(.text.startup+0x12b): undefined reference to `find_subset(int, int, std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status