迭代器

• 為訪問容器提供統一介面
• 資料與演算法分離

為斐波那契數列實現一個簡單的迭代器

• 數列實現

檔案 Fibo.h

#ifndef HEAD_FIBO
#define HEAD_FIBO

#include <vector>
#include "FiboIterator.h"

class Fibo
{
private:
    static std::vector<int> _elems;
    friend int FiboIterator::operator*(); // 友元支援

public:
    Fibo(int size);
    ~Fibo();
    typedef FiboIterator iterator;     // 巢狀型別  

    FiboIterator begin();
    FiboIterator end();
    void display();
};

#endif
 

檔案 Fibo.cpp

#include "Fibo.h"
#include "FiboIterator.cpp"

std::vector<int> Fibo::_elems;
Fibo::Fibo(int size)
{
    for (int i = _elems.size(); i < size; i++)
    {
        if (i < 2)
            _elems.push_back(1);
        else
            _elems.push_back(_elems[i - 1] + _elems[i - 2]);
    }
}

Fibo::~Fibo()
{
}

FiboIterator Fibo::begin()
{
    return FiboIterator(0);
}

FiboIterator Fibo::end()
{
    return FiboIterator(_elems.size());
}

void Fibo::display()
{
    for (auto &&i : _elems)
    {
        std::cout << i << "  ";
    }
    std::cout << std::endl;
}
 

• 迭代器實現

  檔案 FiboIterator.h
  

  #ifndef HEAD_FIBOITERATOR
  #define HEAD_FIBOITERATOR
  
  class FiboIterator
  {
  private:
      int _index;
  
  public:
      FiboIterator(int);
      ~FiboIterator();
  
      bool operator==(const FiboIterator &rhs);
      bool operator!=(const FiboIterator &rhs);
      int operator*();
      FiboIterator &operator++();
      FiboIterator operator++(int);
  };
  
  #endif
   
  

  檔案 FiboIterator.cpp
  

  #include "FiboIterator.h"
  
  class Fibo;
  FiboIterator::FiboIterator(int index) : _index(index - 1)
  {
  }
  
  FiboIterator::~FiboIterator()
  {
  }
  
  bool FiboIterator::operator==(const FiboIterator &rhs)
  {
      return (rhs._index == this->_index);
  }
  
  bool FiboIterator::operator!=(const FiboIterator &rhs)
  {
      return (rhs._index != this->_index);
  }
  int FiboIterator::operator*()
  {
      return Fibo::_elems[_index + 1];
  }
  
  FiboIterator &FiboIterator::operator++()
  {
      _index++;
      return *this;
  }
  
  FiboIterator FiboIterator::operator++(int)
  {
      FiboIterator temp = *this;
      _index++;
      return temp;
  }
  

  測試 main.cpp
  

  #include "Fibo.h"
  #include "Fibo.cpp"
  
  int main()
  {
      Fibo fb(5);
      fb.display();
  
      for (Fibo::iterator it = fb.begin(); it != fb.end(); it++)
      {
          std::cout << "fb:" << *it << std::endl;
      }
  }
  

  == end