2D iterator for loop

Question

I'm having issues implementing an iterator class in regards to .end(). The problem I'm running into is when I try to use a for loop with my iterator class; it's currently stopping just before the last element in a 2D vector. However, I want it to go one element past the last element without causing a compiler error, and to include the last character in the print statement.

main.cpp

// file contents            
// aaa                          
// bbb                          
// cce 

// factory method (adds file contents to 2D <char> vector)
Base *a = Base::create("file");       
cout << *a; // overloaded '<<'

Prints

a a a b b b c c e

Now, when I use a for loop with my iterator class, it doesn't include the last character.

for(auto it = a->begin(); it != a->end(); it++) 
    cout << *it << ' ';

Prints

a a a b b b c c

The .end prints the following

Base::iterator it = aa->end();
cout << *it << '\n';
// prints e

When I try a while loop, it includes the last character.

// Note: my iterator class is a nested class inside Base class.

const Base::iterator et = a->begin(); 
int i = 0;
while(i < 13) {
    cout << *et << ' ';
    et++;
}

Prints

a a a b b b c c e e e e e

I understand that a->end() is supposed to point just past the last character, but I don't understand how to implement that. When I increment past the last value in my operator++(int), it displays a segmentation fault. Currently, my overloaded increment method stops at the last character and doesn't go past it. With that said, how do I implement my ++(int) method to include the last element when printing from a for loop? Am I supposed to add a null element to the vector or something like that?

Inside Base.cpp

// This function is whats causing the issue. I know it looks ugly.
Base::iterator Base::iterator::operator++(int) {

    // base is a Base *, x and y are coordinates for 2D vector
    Base::iterator temp(base, x, y); // save value 

    // if iterator has not reached end
    if( !((x == base->vec.size()-1) && (y == base->vec[0].size()-1)) )
    {
      // if y < row size
      if(y < base->vec[0].size()-1)
          y++;

      // if y has reached end of row, increment x and start y on a new row
      else if(x < base->vec.size() && y == base->vec[0].size()-1) {
          y=0;
          x++;
      }
    }
    return temp;
}

Base::iterator Base::begin() {
    return Base::iterator(this, 0, 0);
}

Base::iterator Base::end() {
    return Base::iterator(this, vec.size()-1, vec[0].size()-1);
}

Rest of Base.cpp

#include "Base.h"

using namespace std;

// Factory method (instantiates 2D vector with file contents)
Base *Base::create(string filename) {/*removed irrelevant code */}

Base::~Base(){}

// prints 2D vector
ostream &operator<<(ostream &os, const Base &val){/*removed irrelevant code*/}

Base::iterator::iterator(Base *b, int m, int n): base(b), x(m), y(n) {}
Base::iterator::~iterator(){}

// returns a character inside 2D vector
char &Base::iterator::operator*() const {
    return base->vec[x][y];
}  

bool Base::iterator::operator==(const Base::iterator& rhs) const {
    return base->vec[x][y] == *rhs;
}

bool Base::iterator::operator!=(const Base::iterator& rhs) const {
    return base->vec[x][y] != *rhs;
}

// Bunch of other functions

Any help would be appreciated.

Answer 1

Base::iterator(this, vec.size()-1, vec[0].size()-1); this will return a valid last element. So you need to change it to Base::iterator(this, vec.size(), 0);, and also update the conditions to switch to a new row in your loop.

Something like:

// if iterator has not reached end
if(x < base->vec.size())
{
  ++y;

  // if y has reached end of row, increment x and start y on a new row
  if(y >= base->vec[0].size() {
      y=0;
      ++x;
  }
}

Also the iterators are wrong:

bool Base::iterator::operator==(const Base::iterator& rhs) const {
    return base == rhs.base && x == rhs.x && y == ris.y;
}

bool Base::iterator::operator!=(const Base::iterator& rhs) const {
    return !(base == rhs.base && x == rhs.x && y == ris.y);
}