foo.cc: In function 'int main()':
foo.cc:11:13: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(max);
             ^
In file included from /usr/include/stdio.h:862:0,
                 from /usr/include/c++/7/cstdio:42,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:46,
                 from foo.cc:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:232:1: note: declared here
 gets (char *__str)
 ^~~~
foo.cc: In function 'void zmin(char*)':
foo.cc:35:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<strlen(a);i++)
              ~^~~~~~~~~~
foo.cc:36:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=i+1;j<strlen(a);j++)
                 ~^~~~~~~~~~
foo.cc: In function 'void zmax(char*)':
foo.cc:42:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<strlen(a);i++)
              ~^~~~~~~~~~
foo.cc:43:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=i+1;j<strlen(a);j++)
                 ~^~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:11:9: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result [-Wunused-result]
     gets(max);
     ~~~~^~~~~
/tmp/ccwJ6ruT.o: In function `main':
foo.cc:(.text.startup+0x29): warning: the `gets' function is dangerous and should not be used.

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。