View Compilation Error

0_0_22689086_13230.cpp: In function 'void Calculate(int, int)':
0_0_22689086_13230.cpp:20:31: error: 'reverse' was not declared in this scope
   reverse(CB.begin(), CB.end());//将CB字符串反转
                               ^
0_0_22689086_13230.cpp: In function 'int main()':
0_0_22689086_13230.cpp:58:33: error: 'reverse' was not declared in this scope
   reverse(SUM.begin(), SUM.end());
                                 ^