/in/foo.cc: In function 'int main()':
/in/foo.cc:7:10: warning: unused variable 'a' [-Wunused-variable]
  int n,i,a;
          ^
/in/foo.cc: In function 'void q_sort(int, int, int*, int)':
/in/foo.cc:30:19: warning: unused variable 'a' [-Wunused-variable]
  int temp,key,i,j,a,b;
                   ^
/in/foo.cc:30:21: warning: unused variable 'b' [-Wunused-variable]
  int temp,key,i,j,a,b;
                     ^