/tmp/ccQ0AHbx.o: In function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'
/tmp/ccExn2U2.o:molecules.cpp:(.text.startup+0x0): first defined here
/tmp/ccExn2U2.o: In function `main':
molecules.cpp:(.text.startup+0x152): undefined reference to `find_subset(int, int, std::vector<int, std::allocator<int> >)'
/tmp/ccQ0AHbx.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