View Compilation Error

0_0_28534567_3303.cpp: In function 'void dfs(int, int)':
0_0_28534567_3303.cpp:12:15: error: 'operate' was not declared in this scope
 for(int i=0;i<operate.size();i++)
               ^
0_0_28534567_3303.cpp:13:17: error: expected primary-expression before '<<' token
 cout<<operate{i}<<"";
                 ^
0_0_28534567_3303.cpp:19:1: error: 'operate' was not declared in this scope
 operate.push_back('i');
 ^
0_0_28534567_3303.cpp:28:1: error: 'operate' was not declared in this scope
 operate.push_back('o');
 ^
0_0_28534567_3303.cpp: In function 'int main()':
0_0_28534567_3303.cpp:38:12: error: 'std::string' has no member named 'lwngth'
 length = a.lwngth();
            ^