foo.cc: In function 'int jud(std::__cxx11::string, std::__cxx11::string, std::__cxx11::string)':
foo.cc:11:25: warning: left operand of comma operator has no effect [-Wunused-value]
     for(i = 0,j = n-1;i <= n-1,j >= 0;i++,j--)
                       ~~^~~~~~
foo.cc:21:9: warning: use of an operand of type 'bool' in 'operator++' is deprecated [-Wdeprecated]
     flag++;break;
         ^~
foo.cc:25:18: warning: use of an operand of type 'bool' in 'operator++' is deprecated [-Wdeprecated]
              flag++;break;
                  ^~
foo.cc:28:12: error: 'mark' was not declared in this scope
         if(mark)//flag为true则为真，停止判断
            ^~~~

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