Valgrind errors in compilation and execution

When I run a program with the valgreend I get the following:

==6153== Invalid read of size 4
==6153==    at 0x401620: estado::n_transiciones() (estadoNFA.cpp:31)
==6153==    by 0x401C82: nfa::mostrar(std::ostream&) (NFA.cpp:96)
==6153==    by 0x402ADB: main (main_nfa.cpp:49)
==6153==  Address 0x38 is not stack'd, malloc'd or (recently) free'd
==6153== 
==6153== 
==6153== Process terminating with default action of signal 11 (SIGSEGV)
==6153==  Access not within mapped region at address 0x38
==6153==    at 0x401620: estado::n_transiciones() (estadoNFA.cpp:31)
==6153==    by 0x401C82: nfa::mostrar(std::ostream&) (NFA.cpp:96)
==6153==    by 0x402ADB: main (main_nfa.cpp:49)
==6153==  If you believe this happened as a result of a stack
==6153==  overflow in your program's main thread (unlikely but
==6153==  possible), you can try to increase the size of the
==6153==  main thread stack using the --main-stacksize= flag.
==6153==  The main thread stack size used in this run was 8388608.
0 ==6153== 

referring to

int estado::n_transiciones(void){
        return ntransiciones_;
    }

And he also complains about this function

ostream& nfa:: mostrar(ostream& os){
        os<<nestados_<<endl;
        os<<estadoarranque_<<endl;
        map<char,set<int> >::iterator it;
        set<int>::iterator ik;
        for(int i=0; i<nestados_;i++){
            os<<i<<" ";

            /*os<<estados_[i].get_aceptacion()<<" ";*/

            os<<estados_[i].n_transiciones()<<" ";

            for(it=estados_[i].get_transiciones().begin(); it!=estados_[i].get_transiciones().end(); it++){
                os<<it->first;
                for(ik= (*it).second.begin(); ik!=(*it).second.end() ; ik++){ //vectorestados[i].get_transiciones().second.end() eso  no, porque cada posicion del map tiene un second, pero el trans_,lo que te devuelve get_transicion, es un conjunto, no tiene second

                    os<<(*ik);
                }
            }
        }

        return os;
    }

the state class NFA hpp

#pragma once
#include<iostream>
#include<map>
#include<vector>
#include<fstream>
#include<string>
#include<set>
#include"estadoNFA.hpp"
using namespace std;
class nfa{
private:
    vector<estado> estados_; // como objeto, pues lo que necesito para cada estado, todos los atributos de estadoNFA
    int nestados_;
    int estadoarranque_;
    bool errorapertura_;
public:
    nfa();

    void leernfa(string nombrefichero);

    ostream& mostrar(ostream& os);

    void estados_importantes(void);

    void estados_muerte(void);

    void esdfa(string nombrefichero);

    void analizarcadena(void);
};

I do not understand the errors of the valgrind

Thanks