View Compilation Error

0_0_14822063_24171.cpp: In function 'std::pair<int, int> bf()':
0_0_14822063_24171.cpp:82:28: error: 'reverse' was not declared in this scope
  reverse(s.begin(), s.end());
                            ^
0_0_14822063_24171.cpp: In function 'void solve()':
0_0_14822063_24171.cpp:98:45: error: 'reverse' was not declared in this scope
  string rs = s; reverse(rs.begin(), rs.end());
                                             ^