foo.cc: In function 'int sub(int*, int*, int, int)':
foo.cc:39:13: error: expected ';' before '}' token
   39 |     return 0//返回差的位数
      |             ^
      |             ;
   40 | 
   41 | }
      | ~            
foo.cc: In function 'bool judge(std::string)':
foo.cc:78:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |     for(int i=0;i<s.size();i++)
      |                 ~^~~~~~~~~
foo.cc: In function 'std::string div(std::string, std::string, int)':
foo.cc:44:12: warning: control reaches end of non-void function [-Wreturn-type]
   44 |     string s,v;//s存商,v存余数
      |            ^

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