/in/foo.cc: In function 'int Hash(char*)':
/in/foo.cc:11:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<=strlen(s+1);i++){
              ~^~~~~~~~~~~~~
/in/foo.cc: In function 'char* substr(char*, int, int)':
/in/foo.cc:20:7: warning: address of local variable 's' returned [-Wreturn-local-addr]
  char s[200]="";int l=0;
       ^
/in/foo.cc: In function 'bool dfs(char*)':
/in/foo.cc:32:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<=strlen(np+1);i++){
              ~^~~~~~~~~~~~~~
/in/foo.cc:57:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^