View Compilation Error

0_0_28534745_2833.cpp: In function 'void dfs(int, int)':
0_0_28534745_2833.cpp:14:23: error: 'operate' was not declared in this scope
         for(int i=0;i<operate.size();i++)
                       ^
0_0_28534745_2833.cpp:15:29: error: expected primary-expression before '<<' token
             cout<<operate{i}<<"";
                             ^
0_0_28534745_2833.cpp:21:5: error: 'operate' was not declared in this scope
     operate.push_back('i');
     ^
0_0_28534745_2833.cpp:30:5: error: 'operate' was not declared in this scope
     operate.push_back('o');
     ^
0_0_28534745_2833.cpp: In function 'int main()':
0_0_28534745_2833.cpp:40:20: error: 'std::string' has no member named 'lwngth'
         length = a.lwngth();
                    ^