foo.cc: In function 'std::string StopFight(std::string)':
foo.cc:10:12: warning: comparison of integer expressions of different signedness: 'int' and 'const size_type' {aka 'const long unsigned int'} [-Wsign-compare]
   10 |  if (index != string::npos)  //如果下标存在
      |      ~~~~~~^~~~~~~~~~~~~~~

Found 10 testcases.
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