molecules.cpp: In function 'void exch()':
molecules.cpp:11:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i=0;i<ans.size();i++){
~^~~~~~~~~~~
molecules.cpp: In function 'std::vector<int> solve(int, int, std::vector<int>)':
molecules.cpp:47:12: warning: division by zero [-Wdiv-by-zero]
cout<<1/0<<endl;
~^~
/tmp/cc1NdgUy.o: In function `main':
grader.cpp:(.text.startup+0x152): undefined reference to `find_subset(int, int, std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status