/in/foo.cc: In function 'int swp(int*, int*)':
/in/foo.cc:18:48: warning: no return statement in function returning non-void [-Wreturn-type]
 int swp(int *a,int *b){int tmp=*a;*a=*b,*b=tmp;}
                                                ^
/in/foo.cc: In function 'void spfa(int)':
/in/foo.cc:34:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<map[T].size();i++){
                     ~^~~~~~~~~~~~~~