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#include <iostream>
#define vector Vector
using namespace std;
template <class T> class My_allocator {
public:
T* allocate(int n); // allocate space for n objects of type T
void deallocate(T* p, int n); // deallocate n objects of type T starting at p
void construct(T* p, const T& v); // construct a T with the value v in p
void destroy(T* p); // destroy the T in p
};
//-------------------------------------------------
template<class T>
T* My_allocator<T>::allocate(int n)
{
T* p = (T*)malloc(sizeof(T)*n);
return p;
}
//------------------------------
template<class T>
void My_allocator<T>::deallocate(T* p, int n)
{
free(p);
}
//------------------------------
template<class T>
void My_allocator<T>::construct(T* p, const T& v)
{
p = new (p) T(v);
}
//------------------------------
template<class T>
void My_allocator<T>::destroy(T* p)
{
p->~T();
}
//------------------------------------------------
class Range_error : out_of_range {
public:
int index;
Range_error(int i) :out_of_range("Range error"), index(i) {}
};
//--------------------------------------------------
template <class T, class A = My_allocator<T> >
class vector{
A alloc;
int sz, space;
T* elem;
public:
vector() :sz(0), space(0), elem(nullptr) {}
vector(int n) :sz(n), space(n) { elem = alloc.allocate(n); initial(T()); }
vector(int n, const T& v) :sz(n), space(n) { elem = alloc.allocate(n); initial(v); }
int size() const { return sz; }
int capacity() const { return space; }
T get_elem(int i) { return elem[i]; }
void initial(const T);
void resize(int, T);
void push_back(const T&);
void reserve(int);
T& operator[](unsigned int n) // rather than return at(i);
{
if (n < 0 || this->sz <= n) throw Range_error(n);
return elem[n];
}
const T& operator[](unsigned int n) const
{
if (n < 0 || this->sz <= n) throw Range_error(n);
return elem[n];
}
};
//------------------------------------------------
template<class T, class A>
void vector<T, A>::initial(const T v)
{
for (int i = 0; i < sz; ++i)
elem[i] = v;
}
//-------------------------------------------
template <class T, class A>
void vector<T, A>::resize(int newsize, T val = T())
{
reserve(newsize);
for (int i = sz; i < newsize; ++i) alloc.construct(&elem[i], val); // construct
for (int i = newsize; i < sz; ++i) alloc.destroy(&elem[i]); // destroy
sz = newsize;
}
//--------------------------------------------
template <class T, class A>
void vector<T, A>::push_back(const T& val)
{
if (space == 0) reserve(8);
else if (sz == space) reserve(2 * space);
alloc.construct(&elem[sz], val);
++sz;
}
//--------------------------------------
template <class T, class A>
void vector<T, A>::reserve(int newalloc)
{
if (newalloc <= space) return;
T* p = alloc.allocate(newalloc);
for (int i = 0; i < sz; ++i) alloc.construct(&p[i], elem[i]);
for (int i = 0; i < sz; ++i) alloc.destroy(&elem[i]);
alloc.deallocate(elem, space);
elem = p;
space = newalloc;
}
//----------------------------------
int main() {
vector<int> v(4,3);
v.push_back(12);
for (int i = 0; i < v.size(); ++i)
cout << "'" << v[i] << "'" << " ";
cout << "\n\n";
v.reserve(10);
for (int i = 0; i < v.size(); ++i)
cout << "'" << v[i] << "'" << " ";
cout << "\n\n";
v.resize(12, 5);
for (int i = 0; i < v.size(); ++i)
cout << "'" << v[i] << "'" << " ";
return 0;
}
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