E9手写Vector和注意事项

最新推荐文章于 2024-12-09 00:31:43 发布

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本文详细介绍了自定义Vector类的设计与实现过程，包括迭代器、容量调整、元素插入删除等功能，并强调了命名空间污染避免、空指针使用、内存复制安全性等问题。

在这里插入图片描述

本来写了一个还可以版本的Vector,然后改了一下用迭代器，然后就从2点查到5点。。。。

#pragma once
#include <string.h>
#include <assert.h>
#include <cmath>
using namespace std;
template<class T>
class Vector {
	typedef T* iterator;
	iterator _begin, _final;
	int _capacity;
public:
	Vector():_begin(nullptr),_final(nullptr),_capacity(0) {

	}
	~Vector() {
		delete[]_begin;
		_begin = nullptr;
		_final = nullptr;
	}
	Vector(const Vector<T>& t) {
		resize(t._capacity);
		for (int i = 0; i < t.size(); i++) {
			_begin[i] = t[i];
		}
		_final = _begin + t.size();
		_capacity = t._capacity;
	}
	void resize(int tocapcity) {
		assert(tocapcity > 0);
		T* newp = new T[tocapcity];
		for (int i = 0; i < min(size(),tocapcity); i++) {//保证截取的有效性
			newp[i] = _begin[i];
		}
		int _size = min(size(),tocapcity);//防止被污染
		_begin =newp;
		_final = _begin + _size;
		_capacity = tocapcity;
		newp = nullptr;
	}
	void push_back(int i) {
		if (size() == capacity()) {
			capacity() == 0 ? resize(2) : resize(2 * _capacity);
		}
		*(_final++) = i;
	}
	
	int size() const{
		return _final - _begin;
	}
	T& operator [](int i) const{
		assert(i >= 0 && i <size());
		return _begin[i];
	}
	T operator [](int i) {
		assert(i >= 0 && i < size());
		return _begin[i];
	}
	bool operator ==(const Vector<T>& v) const{
		bool flag = true;
		if (v.size() == size()) {
			for (int i = 0; i < size(); i++) {
				if ( _begin[i]!=v[i]) {
					flag = false;//只有size相同并且全字匹配才return true
					break;
				}
			}
			return flag;
		}
		else {
			return false;
		}
	}
	iterator& begin() {
		assert(!empty());
		return  _begin;
	}
	iterator& back() {
		assert(!empty());
		return _final;
	}
	int capacity() const{
		return _capacity;
	}
	void clear() {
		_final = _begin;
		//最开始的写法 _final=_begin=nullptr;
	}
	bool empty() const{
		return _final ==_begin;
	}
	void pop_back() {
		assert(!empty());
		_final--;//emm跟stack的处理方式类似
	}
	void erase(iterator from, iterator to) {//前闭后开hh
		assert(from >= _begin && from <= to && to <= _final);
		for (iterator i = to+1;i<=_final; i++) {
			*(i - (to - from)) = *i;
		}
		_final -=(to-from) ;
	}
	void insert(iterator pos, int num, int val) {
		assert(num > 0);
		if (size() + num > _capacity) {//一定要判断是否合法
			resize(size() + num);
		}
		for (iterator i = _final - 1 + num ; i >=pos+num; i--) {
			*i = *(i - num);
		}
		for (iterator i = pos; i < pos + num; i++) {
			*i = val;
		}
		_final += num;
	}
	void insert(iterator pos, int val) {//在pos前插入一个数字val
		insert(pos, 1, val);//委托构造
	}
	void swap( Vector<T>& t) {
		Vector temp = t;
		t = *this;
		*this = temp;
	}
	bool operator >(const Vector<T>& t) const
{
	for (int i = 0; i < min(size(), t.size()); i++)
	{
		if (*(_begin + i) != *(t._begin + i)) {
			return *(_begin + i) > *(t._begin + i);
		}
	}
	return size() > t.size();//字典排序
}
 	bool  operator >=(const Vector<T>& t) const
{
	return   *this == t || *this > t;
}
	bool  operator <(const Vector<T>& t) const
{
	return !(*this >= t);
}
	bool Vector<T>operator <= (const Vector<T>& t) const
{
	return !(this > t);
}
void swap(Vector<T>& v)
{
	std::swap(_begin, v._begin);
	std::swap(_final, v._final);
	std::swap(_capacity, v._capacity);
}
friend istream& operator>>(istream& is, Vector<T>& v)
{
	for (int i = 0; i < v.size(); i++)
	{
		is >> v[i];
	}
	return is;
}
friend ostream& operator<<(ostream& os, Vector<T>& v) {
	for (int i = 0; i < v.size(); i++)
	{
		os << v[i] << endl;
	}
	return os;
}

};