【C++】vector的模拟实现

1. 什么是vector

vector是一个空间可以动态增长的数组。

vector文档说明

2. 模拟实现

#pragma once
#include 
#include 
#include 
#include 
#include 

using namespace std;

namespace lzh {
	template<typename T>
    class vector {
    public:
       // Vector的迭代器是一个原生指针
       typedef T* iterator;
       typedef const T* const_iterator;
       iterator begin() {
           return _start;
       }
       iterator end() {
           return _finish;
       }
       const_iterator begin() const {
           return _start;
       }
       const_iterator end() const {
           return _finish;
       }

       // construct and destroy
	//初始化列表给指针置空或者给缺省值
       vector() { 
	
	}

       vector(int n, const T& val = T()) {
           resize(n, val);
       }

       template<class InputIterator>
       vector(InputIterator first, InputIterator last) {
           while (first != last) {
               push_back(*first);
               ++first;
           }
       }

       /*vector(const vector& v) {
           _start = new T[v.size()];
           for (size_t i = 0; i < v.size(); ++i) {
               _start[i] = v._start[i];
           }
           _finish = _start + v.size();
           _endOfStorage = _start + v.capacity();
       }*/

       vector(const vector<T>& v) {
           reserve(v.size());
           for (auto& i : v) {
               push_back(i);
           }
       }

       void swap(vector<T>& v) {
           std::swap(_start, v._start);
           std::swap(_finish, v._finish);
           std::swap(_endOfStorage, v._endOfStorage);
       }

       vector<T>& operator= (vector<T> v) {
           swap(v);
		   return *this;
       }

       ~vector() {
           if (_start) {
               delete[] _start;
               _start = _finish = _endOfStorage = nullptr;
           }
       }

       // capacity
       size_t size() const {
           return _finish - _start;
       }

       size_t capacity() const {
           return _endOfStorage - _start;
       }

       void reserve(size_t n) {
           if (n > capacity()) {    
               T* temp = new T[n];
               size_t oldSize = size();
               if (_start) {
                   for (size_t i = 0; i < oldSize; ++i) {
                       temp[i] = _start[i];
                   }
                   delete[] _start;
               }
               _start = temp;
               _finish = temp + oldSize;
               _endOfStorage = temp + n;
           }
       }

       void resize(size_t n, const T& val = T()) {
           size_t _size = size();
           if (n > _size && n - _size > (size_t)(_endOfStorage - _finish)) {
               reserve(n);
           }
           while (_size < n) {
               push_back(val);
               ++_size;
           }
           _finish = _start + n;
       }

       ///access///
       T& operator[](size_t pos) {
           assert(_start + pos < _finish);
           return _start[pos];
       }
       const T& operator[](size_t pos)const {
           assert(_start + pos < _finish);
           return _start[pos];
       }

       ///modify/
       void push_back(const T& x) {
           /*if (_finish == _endOfStorage) {
               size_t _capacity = capacity();
               reserve(_capacity ? _capacity * 2 : 1);
           }
           _finish[0] = x;
           ++_finish;*/
           insert(end(), x);
       }

       void pop_back() {
           assert(_finish);
           --_finish;
       }

       iterator insert(iterator pos, const T& x) {
           assert(pos >= _start && pos <= _finish);

           //迭代器失效
           if (_finish == _endOfStorage) {
               size_t len = pos - _start;
               size_t _capacity = capacity();
               reserve(_capacity ? _capacity * 2 : 1);
               pos = _start + len;
           }
           iterator end = _finish;
           while (end > pos) {
               end[0] = end[-1];
               --end;
           }
           pos[0] = x;
           ++_finish;
           return pos;
       }

       iterator erase(iterator pos) {
           assert(pos < _finish);
           iterator end = pos;
           while (end < _finish) {
               end[0] = end[1];
               ++end;
           }
           --_finish;
           return pos;
       }

    private:
        iterator _start = nullptr; // 指向数据块的开始
        iterator _finish = nullptr; // 指向有效数据的尾
        iterator _endOfStorage = nullptr; // 指向存储容量的尾
    };
}