/in/foo.cc: In function 'void Spfa()':
/in/foo.cc:40:11: warning: unused variable 'k' [-Wunused-variable]
     int j,k,MAX,x,headz=0,tailz=1;
           ^
/in/foo.cc:40:13: warning: unused variable 'MAX' [-Wunused-variable]
     int j,k,MAX,x,headz=0,tailz=1;
             ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:60:47: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
 void add(int x,int y,int id) {son[++E[id]][id]=y;nxt[E[id]][id]=lnk[x][id];lnk[x][id]=E[id];}
                               ~~~~~~~~~~~~~~~~^~
/in/foo.cc:63:15: note: 'y' was declared here
     int i,j,x,y,fi,fj;
               ^
/in/foo.cc:60:74: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
 void add(int x,int y,int id) {son[++E[id]][id]=y;nxt[E[id]][id]=lnk[x][id];lnk[x][id]=E[id];}
                                                                 ~~~~~~~~~^
/in/foo.cc:63:13: note: 'x' was declared here
     int i,j,x,y,fi,fj;
             ^