/in/P4.cpp: In function 'int main()':
/in/P4.cpp:62:23: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for (int i = 0; i < nums.size(); ++i) {
                     ~~^~~~~~~~~~~~~
/in/P4.cpp:21:9: error: unused variable 'n' [-Werror=unused-variable]
     int n;                  // 数组大小
         ^
cc1plus: all warnings being treated as errors