/in/foo.c: In function 'main':
/in/foo.c:7:3: warning: implicit declaration of function 'memset' [-Wimplicit-function-declaration]
   memset(dis,0,sizeof(dis));
   ^~~~~~
/in/foo.c:7:3: warning: incompatible implicit declaration of built-in function 'memset'
/in/foo.c:7:3: note: include '<string.h>' or provide a declaration of 'memset'
/in/foo.c: In function 'dfs':
/in/foo.c:34:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^