foo.cc:12:12: warning: 'judgement' initialized and declared 'extern'
 extern int judgement=0;
            ^
foo.cc: In function 'bool isInteger(char*)':
foo.cc:81:25: error: 'strlen' was not declared in this scope
     size_t len=strlen(ch);
                         ^
foo.cc:84:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=1;i<len;i++)
                      ^
foo.cc:89:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(k==len-1)
             ^
foo.cc:95:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<len;i++)
                      ^
foo.cc:100:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(k==len)
             ^

自豪的采用 HydroJudger 进行评测(github.com/hydro-dev/HydroJudger)