/in/foo.cc: In function 'void init()':
/in/foo.cc:10:15: warning: unused variable 'k' [-Wunused-variable]
     int i, j, k, x, y, z;
               ^
/in/foo.cc: In function 'int SPFA(int, int)':
/in/foo.cc:35:15: warning: unused variable 'k' [-Wunused-variable]
     int i, j, k, front, rear;
               ^