Tell compiler to look for include files

I'm trying to extend someone's work, but without success in including his header files appropriately. Namely, I compile the code by using

Code:

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g++ -o myprog $(pkg-config --cflags --libs libgraph libgvc cairo) source.cpp source.c

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Now, I need to use the $ROOT/lib somehow to to tell the compiler to look in my
ROOT directory for include files. How should my new code used for compilation look like?

Thanks.

If headers are in $ROOT/include and libs in $ROOT/lib then just add "-I$ROOT/include -L$ROOT/lib" to the command.