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从C++开始的编程生活（12）——vector简单介绍和迭代器

news 2025/11/12 9:27:12

前言

本系列文章承接C语言的学习，需要有C语言的基础才能学会哦~
第12篇主要讲的是有关于C++的vector简单介绍和迭代器失效。
C++才起步，都很简单！！

前言

vector

基本接口

assign赋值

insert插入

ps：

vector底层实现

迭代器失效

vector

是C++的顺序容器，也就是顺序表，是模板，需要模板参数。

vector的构造，析构等基本接口与string用法基本相同，这里不加赘述，

基本接口

assign赋值

v1.assign( {10,20,30} );

覆盖原本内容，若超出容量会扩容。

insert插入

v1.insert(v1.begin(), 9);

vector的插入不支持直接靠下标插入，需要通过指针加减指向插入位置。

ps：

vector扩容在vs下以1.5倍扩容。

其他接口功能、迭代器等与string相似性很高，了解string的用法即可举一反三到vector中使用。

String参考文章《--------点击学习

vector底层实现

#pragma once
#include<assert.h>
namespace bit
{template<class T>class vector{public: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;}vector():_start(nullptr), _finish(nullptr), _endofstorage(nullptr){	}vector(initializer _list<T> il):_start(nullptr), _finish(nullptr), _endofstorage(nullptr){	reserve(li.size());for (auto e : li){push_back(e);}}template <class InputIterator>vector(InputIterator first, InputIterator last){while (first != last){push_back(*first);++first;}}vector(size_t n, const T& val = T()){reserve(n);for (size_t i = 0; i < n; i++){push_back(val);}}vector(int n, const T& val = T()){reserve(n);for (int i = 0; i < n; i++){push_back(val);}}vector(initializer _list<T> il){reserve(il.size());for (auto& e : li){push_back(e);}}vector(const vector<T>& v){reserve(v.capacity());for (auto& e : v){push_back(e);}}void swap(vector<T>& tmp){std::swap(_start, tmp._start);std::swap(_finish, tmp._finish);std::swap(_endofstorage, tmp._endofstroage);}vector<T>& operator=(vector<T> v){swap(v);return *this;}~vector(){if (_start){delete[] _start;_start = _finish = _endofstorage = nullptr;}}T& operator[](size_t i){assert(i < size());return _start[i];}const T& operator[](size_t i) const{assert(i < size());return _start[i];}size_t size()const{return _finish - _start;}size_t capacity() const{return _endofstorage - _start;}void resize(size_t n, T val = T()){if (n > capacity()){_finish = _start + n;}else{reserve(n);while (_finish < _start + n){*_finish = val;++_finish;}}}void reserve(size_t n){if (n > capacity()){size_t oldSize = size();T* tmp = new T[n];if (_start){//memcpy(tmp, _start, sizeof(T) * oldSize);for (size_t i = 0; i < oldSize; i++){tmp[i] = _start[i];}delete[] _start;}_start = tmp;_finish = _start + oldSize;_endofstorage = _start + n;}}void push_back(const T& x){if (_finish == _endofstorage){reserve(capacity() == 0 ? 4 : capacity() * 2);}*finish = x;++_finish;}bool empty(){return _start == _finish;}void pop_back(){assert(!empty());--_finish;}iterator insert(iterator pos, const T& x){assert(pos >= _start && pos < _finish);if (_finish == _endofstorage){size_t len = pos - _start;reserve(capacity() == 0 ? 4 : capacity() * 2);pos = _start + len;}iterator i = _finish - 1;while (i >= pos){*(i + 1) = *i;--i;}*pos = x;++_finish;return pos;}iterator erase(iterator pos){assert(pos >= _start);assert(pos < _finish);iterator i = pos + 1;while (i < _finish){*(i - 1) = *i;++i;}_finish--;return pos;}private:iterator _start = nullptr;iterator _finish = nullptr;iterator _endofstorage = nullptr;};
}