/in/foo.cc: In function 'bool SPFA()':
/in/foo.cc:48:22: warning: 'tb' may be used uninitialized in this function [-Wmaybe-uninitialized]
     int x,Low=INF,ta,tb;
                      ^~
/in/foo.cc:48:19: warning: 'ta' may be used uninitialized in this function [-Wmaybe-uninitialized]
     int x,Low=INF,ta,tb;
                   ^~