Compile Error
/in/foo.cc:20:27: error: ISO C++ forbids declaration of 'add_edge' with no type [-fpermissive] add_edge(int u,int v,int w) ^ /in/foo.cc: In function 'int add_edge(int, int, int)': /in/foo.cc:26:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^