c++ vector模拟实现代码

#include<iostream>
using namespace std;
namespace bit
{
 template<typename T>
 class vector
 {
 public:
 typedef T* iterator;
 public:
 T operator[](int i)
 {
  return start[i];
 }
 public:
 vector() :start(nullptr), finish(nullptr), end_of_sorage(nullptr)
 {
 }
 vector(size_t n, const T& value = T()) :start(nullptr), finish(nullptr), end_of_sorage(nullptr)
 {
  reserve(n);//先扩容
  while (n--!=0) //再填充
  {
  push_back(value);
  }
 }
 template<class InPutIterator> //由前后指针来创建
 vector(InPutIterator first, InPutIterator last):start(nullptr), finish(nullptr), end_of_sorage(nullptr)
 {
  reserve(last-first);//先申请空间
  while (first != last)
  {
  push_back(*first);
  first++;
  }
 }
 ~vector()
 {
  delete[]start;
  start = finish = end_of_sorage = nullptr;
 }
 public:
 int size()
 {
  return finish - start;
 }
 int capacity()
 {
  return end_of_sorage - start;
 }
 bool empty()
 {
  return finish == start;
 }
 void swap(vector<T>& v)
 {
  std::swap(start, v.start);
  std::swap(finish, v.finish);
  std::swap(end_of_sorage, v.end_of_sorage);
 }
 void reserve(size_t new_capacity) // 扩容
 {
  if (new_capacity > capacity())
  {
  int old_size = size(); //原来的大小 
  T* newV = new T[new_capacity]; //新申请空间
  if (start)//当原有内容不空时
  {
   for (int i = 0; i < size(); i++) //复制进新空间
   {
   newV[i] = start[i];
   }
  }
  delete[]start;//删除原有空间
  start = newV;//指向新空间
  finish = start + old_size;
  end_of_sorage = start + new_capacity;
  }
 }
 void resize(int new_size, const T& value = 0) //扩充大小
 {
  if (new_size <= size())
  {
  finish = start + new_size;
  }
  if (new_size > capacity())
  {
  reserve(new_size * 2);
  }
  iterator p = finish;
  finish = start + new_size;//指向新大小
  while (p != finish) //填充value
  {
  *p = value;
  p++;
  }
 }
 public:
 void push_back(const T &c)
 {
  insert(end(), c);
 }
 public:
 typedef T* iterator;
 iterator begin()
 {
  return start;
 }
 iterator end()
 {
  return finish;
 }
 public:
 iterator insert(iterator pos, const T &x) //在pos位置前插入x
 {
  if (size() + 1 >= capacity())
  {
  size_t oldpos = pos - start;
  size_t new_capacity = capacity() ? (capacity() * 2) : 1;
  reserve(new_capacity);
  pos = start + oldpos;
  }
  T* p = finish;
  for (; p != pos; p--)
  {
  *p = *(p - 1);
  }
  *p = x;
  finish++;
  return pos;
 }
 iterator erase(iterator pos) //删除pos位置值
 {
  T* p = pos;
  while (p != finish - 1)
  {
  *p = *(p + 1);
  p++;
  }
  finish--;
  return pos;
 }
 private:
 T* start;//指向最开始
 T* finish;//指向最后一个元素的下一个位置
 T* end_of_sorage;//指向最大容量的下一个位置
 };
}
int main()
{
 int ar[] = { 1,2,3,4,5,6,7,7 };
 bit::vector<int>v1(ar, ar + 6);
 bit::vector<int>v2;
 bit::vector<int>v3(10,'a');
 v1.erase(v1.end()-1);
 v1.insert(v1.begin(), 0);
 v1.swap(v3);
 for (int i = 0; i < v1.size(); i++)
 {
 cout << v1[i] << " ";
 }
 return 0;
}