How to initialize a pointer to a structure in C++? -

here defined structure struct structure in class a. class b nested in class a.

class { public:         struct structure            // structure need      {         std::vector <std::vector <float>>         input;         std::vector <int>                         output;         float                                     ft;            b*                                        bb;     }; private:         b             b;     structure*    pstruct;                 }; 

now want initialize pointer pstruct before use it.
example, use pstruct->output.push_back().

for example can initialize pointer in default constructor of class. like

class b {};  class     {      public:          a() : b(), pstruct( new structure() ) { pstruct->bb = &b; }                 struct structure            // structure need           {           std::vector <std::vector <float>>         input;           std::vector <int>                         output;           float                                     ft;            b*                                        bb;          };      private:               b             b;           structure*    pstruct;                     };