我有一个采用通用序列的方法,然后从该序列获得一个偏移量,从而创建一个堆栈:
template <typename IterT>
stack(IterT begin, IterT end) : _stack(0), _size(0), _capacity(0) {
try {
for(; begin!=end; ++begin) {
push(static_cast<T>(*begin));
}
}
catch(...) {
clear(); //my method to destroy the stack
throw;
}
}
我主要执行以下操作:
int a[5] = {1, 2, 3, 4, 5};
stack<int> sint(a, a+5);
cout << sint << endl;
但是,当代码运行时,将创建堆栈但不打印堆栈。有人可以帮我吗?还要给我其他帮助(有关代码缩进,改进等)。谢谢,我将转发迭代器代码。
class const_iterator {
const T* data;
unsigned int index;
public:
typedef std::forward_iterator_tag iterator_category;
typedef T value_type;
typedef ptrdiff_t difference_type;
typedef const T* pointer;
typedef const T& reference;
const_iterator() : data(0){}
const_iterator(const T* arr) : data(arr) {}
const_iterator(const const_iterator &other)
: data(other.data){ }
const_iterator& operator=(const const_iterator &other) {
data = other.data;
return *this;
}
~const_iterator() {
data = 0;
}
reference operator*() const {
return *data;
}
pointer operator->() const {
return &(data);
}
const_iterator operator++(int) {
const_iterator tmp(*this);
++*this;
return tmp;
}
const_iterator& operator++() {
++data;
return *this;
}
bool operator==(const const_iterator &other) const {
return data[index] == other.data[index];
}
bool operator!=(const const_iterator &other) const {
return data[index] != other.data[index] ;
}
private:
friend class stack;
const_iterator(unsigned int ind) :
index(ind){}
}; // class const_iterator
const_iterator begin() const {
cout << "begin" << _stack[_size-1] << endl;
return const_iterator(_stack[_size-1]);
}
const_iterator end() const {
cout << "end" << _stack[0] << endl;
return const_iterator(_stack[0]);
}
最后但并非最不重要的一点是,我重新定义了<<操作符以适合迭代器:
template <typename T>
std::ostream &operator<<(std::ostream &os, const stack<T> &st) {
typename stack<T>::const_iterator i, ie;
for(i = st.begin(), ie = st.end(); i!=ie; ++i){
os << *i << std::endl;
}
return os;
}
以下是堆栈的代码(为便于阅读,我省略了一些内容。)
stack()
: _capacity(0), _size(0), _stack(0){}
void push (const T &value){
if (_size == _capacity){ //raddoppio la dimensione
if(_capacity == 0)
++_capacity;
_capacity *= 2;
T* tmp = new T[_capacity];
copy_n(_stack, _size, tmp);
swap(_stack, tmp);
delete[] tmp;
}
_stack[_size] = value;
++_size;
}
void pop(){
T _tmp;
if(!is_empty()){
_tmp = _stack[_size-1];
--_size;
}
}
答案 0 :(得分:1)
如果您要创建一个看起来像指针的迭代器,则不需要index
,因为data
会发挥作用。比较运算符应该比较data
,而不是值:
bool operator==(const const_iterator &other) const {
return data == other.data;
}
如果要创建reverse iterator,则稍微复杂一些。首先,operator++
应该减少data
。其次,取消引用运算符应不返回*data
,而应返回*(data - 1)
。第三,data
迭代器中的begin()
应指向stack[size]
,data
迭代器中的end()
应指向stack[0]
。无论如何,您都不需要析构函数。
答案 1 :(得分:0)
我遵循了先前的建议,这是经过编辑的结果,但仍然无法弄清如何在专用部分中正确使用构造函数
class const_iterator {
const T *data;
public:
/* ITERATOR TRAITS HERE */
const_iterator() : data(0){}
const_iterator(const T* arr) : data(arr) {}
const_iterator(const const_iterator &other)
: data(other.data){ }
const_iterator& operator=(const const_iterator &other) {
data = other.data;
return *this;
}
~const_iterator() {
data = 0;
}
reference operator*() const {
return *data;
}
pointer operator->() const {
return &(data);
}
const_iterator operator++(int) {
const_iterator tmp(*this);
++*this;
return tmp;
}
const_iterator& operator++() {
++data;
return *this;
}
bool operator==(const const_iterator &other) const {
return data == other.data;
}
bool operator!=(const const_iterator &other) const {
return data != other.data;
}
private:
friend class stack;
const_iterator(const T *d) {
data = d;
}
}; // classe const_iterator
const_iterator begin() const {
return const_iterator(_stack[_size-1]);
}
const_iterator end() const {
return const_iterator(_stack[0]);
}