我正在尝试实现我的stl-like容器，它实际上将是一个不完整的地图版本.在实现擦除方法的时候面临一个问题，我不明白如何删除一对 <key, value>.我被卡住了，所以我请求帮助。谁能指导我解决这个问题？下面是代码.P.S.：我才开始学习C++。
void erace(const key_type& Key)
{
int n = 1;
for (iterator i = begin(); i != end(); ++i, n++)
{
if (i->first == Key)
{
//TO DO.
}
}
}
整段代码.P.S.：我才开始学习C++；整段代码。
template < typename Key, typename T, typename Compare = std::less<Key>, typename Allocator = std::allocator< std::pair<const Key, T> > >
class map
{
public:
class miterator
{
public:
typedef miterator self_type;
typedef std::pair<const Key, T> value_type;
typedef std::pair<const Key, T>& reference;
typedef std::pair<const Key, T>* pointer;
typedef std::bidirectional_iterator_tag iterator_category;
typedef std::ptrdiff_t difference_type;
miterator(pointer ptr) : ptr_(ptr) { };
miterator() {}
self_type operator=(const self_type& other) { ptr_ = other.ptr_; return *this; }
self_type operator++() { self_type i = *this; ptr_++; return i; }
self_type operator--() { self_type i = *this; ptr_--; return i; }
self_type operator++(int junk) { ptr_++; return *this; }
self_type operator--(int junk) { ptr_--; return *this; }
reference operator*() { return *ptr_; }
pointer operator->() { return ptr_; }
pointer operator&() { return ptr_; }
bool operator==(const self_type& rhs) { return ptr_ == rhs.ptr_; }
bool operator!=(const self_type& rhs) { return ptr_ != rhs.ptr_; }
private:
pointer ptr_;
};
class mconst_iterator
{
public:
typedef mconst_iterator self_type;
typedef std::pair<const Key, T> value_type;
typedef std::pair<const Key, T>& reference;
typedef std::pair<const Key, T>* pointer;
typedef std::ptrdiff_t difference_type;
typedef std::bidirectional_iterator_tag iterator_category;
mconst_iterator(pointer ptr) : ptr_(ptr) { };
mconst_iterator() {}
self_type operator=(const self_type& other) { ptr_ = other.ptr_; return *this; }
self_type operator++() { self_type i = *this; ptr_++; return i; }
self_type operator--() { self_type i = *this; ptr_--; return i; }
self_type operator++(int junk) { ptr_++; return *this; }
self_type operator--(int junk) { ptr_--; return *this; }
reference operator*() { return *ptr_; }
pointer operator->() { return ptr_; }
pointer operator&() { return ptr_; }
bool operator==(const self_type& rhs) { return ptr_ == rhs.ptr_; }
bool operator!=(const self_type& rhs) { return ptr_ != rhs.ptr_; }
pointer ptr_;
};
typedef map<Key, T, Compare, Allocator> mymap;
typedef Key key_type;
typedef T mapped_type;
typedef std::pair<const Key, T> value_type;
typedef std::size_t size_type;
typedef std::ptrdiff_t difference_type;
typedef Compare key_compare;
typedef Allocator allocator_type;
typedef value_type& reference;
typedef const value_type& const_reference;
typedef value_type* pointer;
typedef const value_type* const_pointer;
typedef miterator iterator;
typedef mconst_iterator const_iterator;
typedef std::reverse_iterator<miterator> reverse_iterator;
typedef std::reverse_iterator<mconst_iterator> const_reverse_iterator;
map()
: size(0), capacity(20), data(Allocator().allocate(20))
{
}
map(const mymap& _Rhs)
: size(_Rhs.size), capacity(_Rhs.size + 20), data(Allocator().allocate(_Rhs.size))
{
int count = 0;
for (iterator i = &_Rhs.data[0]; i != &_Rhs.data[_Rhs.size]; ++i, ++count)
{
Allocator().construct(&data[count], *i);
}
}
~map()
{
if (!empty())
{
Allocator().deallocate(data, capacity);
}
}
mymap& insert(const value_type& pair)
{
if (!is_present(pair))
{
if (++size >= capacity)
{
reserve(capacity * 2);
}
Allocator().construct(&data[size - 1], pair);
return *this;
}
}
bool is_present(const value_type& pair)
{
for (iterator i = begin(); i != end(); ++i)
{
if (i->first == pair.first)
{
return true;
}
return false;
}
}
bool has_key(const key_type& _Key)
{
for (iterator i = begin(); i != end(); ++i)
{
if (i->first == _Key)
{
return true;
}
}
return false;
}
mapped_type& operator[](const key_type& _Key)
{
if (has_key(_Key))
{
for (iterator i = begin(); i != end(); ++i)
{
if (i->first == _Key)
{
return i->second;
}
}
}
size_type op = size;
insert(value_type(_Key, mapped_type()));
return data[op].second;
}
mymap& reserve(size_type _Capacity)
{
int count = 0;
if (_Capacity < capacity)
{
return *this;
}
pointer buf = Allocator().allocate(_Capacity);
for (iterator i = begin(); i != end(); ++i, ++count)
{
Allocator().construct(&buf[count], *i);
}
std::swap(data, buf);
Allocator().deallocate(buf, capacity);
capacity = _Capacity;
return *this;
}
void erace(const key_type& Key)
{
int n = 1;
for (iterator i = begin(); i != end(); ++i, n++)
{
if (i->first == Key)
{
//TO DO
}
}
}
size_type get_size() const { return get_size; }
bool empty() const
{
return size == 0;
}
iterator clear()
{
~map();
}
iterator begin()
{
return &data[0];
}
iterator end()
{
return &data[size];
}
reverse_iterator rbegin()
{
return &data[0];
}
reverse_iterator rend()
{
return &data[size];
}
const_iterator cbegin() const
{
return &data[0];
}
const_iterator cend() const
{
return &data[size];
}
const_reverse_iterator rbegin() const
{
return &data[0];
}
const_reverse_iterator rend() const
{
return &data[size];
}
iterator find(const key_type& Key)
{
for (iterator i = begin(); i != end(); ++i)
{
if (i->first == Key)
{
return i;
}
}
iterator res = end();
return res;
}
private:
pointer data;
size_type size, capacity;
};
由于你把地图表示为一个数组的对，这和从数组中擦除一个元素是一样的。
由于顺序并不重要，你可以把最后一个元素和你要删除的元素交换，然后销毁删除的元素，调整大小。