由于我们之前已经详细讲解了string接口,而vector接口大都在string上有,所以大家只需自行翻阅前面文章就可以明白接口的使用了,所以,这里我们只实现vector,注意:vector会有迭代器失效的情况,大家一定要仔细看看代码。
#pragma once
#include <assert.h>
#include <iostream>
#include <string.h>
namespace cx
{
//模板类
template<class T>
class vector
{
public:
typedef T* iterator;
typedef const T* const_iterator;
//构造函数:
vector()
{}
//传统写法
/*vector(const vector<T>& v)
{
_start = new T[v.capacity()];
memcpy(_start, v._start, v.size() * sizeof(T));
_finish = _start + v.size();
_endofstorage = _start + v.capacity();
}*/
//现代写法:
vector(const vector<T>& v)
{
reserve(v.capacity());
for (const auto e : v)
{
*_finish = e;
_finish++;
}
}
vector(size_t n, const T& val = T())
{
resize(n,val);
}
/*template <class InputIterator>
vector(InputIterator first, InputIterator last)
{
while (first != last)
{
push_back(*first);
first++;
}
}*/
//析构函数
~vector()
{
if (_start)
{
delete[] _start;
_start = _finish = _endofstorage = nullptr;
}
}
vector<T>& operator=(vector<T> v)
{
swap(v);
return *this;
}
//迭代器
iterator begin()
{
return _start;
}
iterator end()
{
return _finish;
}
const_iterator begin()const
{
return _start;
}
const_iterator end()const
{
return _finish;
}
//计算大小
size_t size()const
{
return end() - begin();
}
size_t capacity()const
{
return _endofstorage - _start;
}
//操作:
bool empty() const
{
return _finish == _start;
}
void swap(vector<T>& v)
{
std::swap(_start, v._start);
std::swap(_finish, v._finish);
std::swap(_endofstorage, v._endofstorage);
}
void reserve(size_t n)
{
if (n > capacity())
{
size_t old = size();
T* tmp = new T[n];
if (_start)
{
memcpy(tmp, _start, sizeof(T) * old);
delete[] _start;
}
_start = tmp;
_finish = _start + old;
_endofstorage = _start + n;
}
}
void push_back(const T x)
{
//检查是否扩容
if (_finish == _endofstorage)
{
size_t newcapacity = capacity() == 0 ? 4 : 2 * capacity();
reserve(newcapacity);
}
*_finish = x;
_finish++;
}
void pop_back()
{
assert(size() > 0);
_finish--;
}
T& operator[](size_t pos)
{
assert(pos < size());
return _start[pos];
}
T& operator[] (size_t pos) const
{
assert(pos < size());
return _start[pos];
}
iterator insert(iterator pos, const T& val)
{
assert(pos <= _finish && pos >= _start);
if (_finish == _endofstorage)
{
size_t len = pos - _start;
reserve(capacity() == 0 ? 4 : 2 * capacity());
pos = _start + len;
}
//memmove(pos + 1, pos, sizeof(T) * (_finish - pos));
iterator end = _finish - 1;
while (end >= pos)
{
*(end + 1) = *(end);
end--;
}
*pos = val;
_finish++;
return pos;
}
/*void insert(iterator pos, const T& x)
{
//检查
assert(pos >= _start);
assert(pos <= _finish);
if (_finish == _endofstorage)
{
size_t len = pos - _start;
reserve(capacity() == 0 ? 4 : 2 * capacity());
//注意:pos位置也要改变
pos = _start + len;
}
memmove(pos + 1, pos, sizeof(T) * (_finish - pos));
*pos = x;
_finish++;
}*/
iterator erase(iterator pos)
{
assert(pos < _finish && pos >= _start);
iterator it = pos + 1;
while (it < _finish)
{
*(it - 1) = *it;
it++;
}
_finish--;
return pos;
}
iterator erase(iterator first, iterator last)
{
}
void resize(size_t n, T val = T())
{
if (n > size())
{
reserve(n);
while (_finish < _start + n)
{
*_finish = val;
_finish++;
}
}
else
{
_finish = _start + n;
}
}
T& front()
{
return *_start;
}
const T& front() const
{
*_start;
}
T& back()
{
return *_finish;
}
const T& back() const
{
return *_finish;
}
T& at(size_t pos)
{
assert(pos < size());
return _start[pos];
}
const T& at(size_t pos) const
{
assert(pos < size());
return _start[pos];
}
void assign(size_t n, const T& val)
{
assert(_start == _finish);
reserve(n);
while (_finish != _endofstorage)
{
*_finish = val;
_finish++;
}
}
void clear()
{
resize(0);
}
private:
iterator _start = nullptr;
iterator _finish = nullptr;
iterator _endofstorage = nullptr;
};
}
最后,感谢大家的支持!