/in/foo.cc: In function 'int main()':
/in/foo.cc:9:11: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(k);//读入整行，k是明码 
           ^
In file included from /usr/include/c++/7/cstdio:42:0,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:10:11: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(s);//s是密文 
           ^
In file included from /usr/include/c++/7/cstdio:42:0,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:19:20: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
         ans[i]=s[i]-j;//得到密文所对应的明文字母
                ~~~~^~
/tmp/cculrnbE.o: In function `main':
foo.cc:(.text.startup+0xe): warning: the `gets' function is dangerous and should not be used.