Vector和List的使用

一、vector

       vector像一个容器一样可以存放各种类型的对象，它是一个能够存放任意类型的动态数组，能够增加和压缩数据。使用vector，需要在头文件中包含#include <vector>

1、简单模拟实现vector:

void print_vector(const vector<int>& v)//迭代器失效{vector<int>::const_iterator it = v.begin();while (it != v.end()){cout << *it << " ";++it;}cout << endl;}void test_vector1(){vector<int> v1;v1.push_back(1);v1.push_back(2);v1.push_back(3);v1.push_back(4);print_vector(v1);//解决迭代器的失效vector<int>::iterator it1 = v1.begin();while (it1 != v1.end()){if (*it1 % 2 == 0){it1 = v1.erase(it1);}else{++it1;}}print_vector(v1);vector<int>::iterator pos1 = find(v1.begin(), v1.end(), 3);v1.insert(pos1, 5);print_vector(v1);pos1 = find(v1.begin(), v1.end(), 3);v1.erase(pos1);print_vector(v1);}


template<class T>class Vector{public:typedef T* Iterator;Vector():_start(NULL), _finish(NULL), _endOfStorage(NULL){}Vector(int n, const T* data = T()):_start(NULL), _finish(NULL), _endOfStorage(NULL){_start = new T(n);for (size_t i = 0; i < n; ++i){_start[i] = data;}_finish = _start + n;_endOfStorage = _finish;}Vector(const vector<T>& v):_start(NULL), _finish(NULL), _endOfStorage(NULL){size_t size = Size();v.size = new T[size];for (size_t i = 0; i < size; ++i){v._start[i] = _start;}_finish = _start + size;_endOfStorage = _finish;}~Vector(){if (_start){delete[] _start;_start = _finish = _endOfStorage = NULL;}}void Resize(size_t n, const T& val = T()){if (n > Capacity()){Expand(n);}size_t size = Size();if (n < size){_finish = _start + n;}else{for (size_t i = 0; i < n - _size, ++i){PushBack(val);}}}void Reserve(size_t n){Expend(n);}void PopBack(){assert(_finish > _start);--_finish;}void PushBack(const T& x){if (_finish == _endOfStorage){size_t capacity = Capacity();size_t n = capacity == 0 ? 3 : 2 * capacity;Expand(n);}*_finish = x;++_finish;}Iterator Begin(){return _start;}Iterator End(){return _finish;}size_t Capacity(){return _endOfStorage - _start;}size_t Size(){return _finish - _start;}void Expand(size_t n){size_t capacity = Capacity();size_t size = Size();if (n > capacity){T* tmp = new T[n];for (size_t i = 0; i < size; ++i){tmp[i] = _start[i];}delete[] _start;_start = tmp;_finish = _start + size;_endOfStorage = _start + n;}}T& operator[](size_t index){assert(index < Size());return _start[index];}//重载const T& operator[](size_t index)const{assert(index < Size());return _start[index];}protected:Iterator _start;Iterator _finish;Iterator _endOfStorage;};
2、这里着重说明一下vector的成员函数resize和 reserve的作用和区别：
   （1）、reserve与capacity息息相关，当reserve(n),n>capacity,将capacity增容到n，否则不变；resize与size息息相关，resize(n),size变为n，而capacity是否改变取决于n是否大于capacity。
   （2）、reserve()增容是先增容，再将以前的数据拷过去，不断重复，不断扩大，代价大，因此使用reserve()函数会提前设定容量大小，只要不超过它的最大容量，它可以自动增长以容纳你的所有数据；而resize()可以直接增容到想要的空间。
   （3）、reserve()搭配push_back()顺序插入数据；resize()搭配operator[]可以初始化和随机插入。
他们的共同作用是减少增容，提高vector的效率。
二、list
      list是标准STL中的序列式容器，它里面的元素是有序的线性序列，可以进行快速的插入删除，可以存放任何数据类型，包括指针，但是不支持随机访问。list是一个双向循环列表，其中的元素通过迭代器遍历。
简单模拟实现list：
#pragma once#include <cassert>#include <list>#include <iostream>using namespace std;template <class T>struct ListNode//链表节点{T _data;ListNode<T>* _prev;ListNode<T>* _next;ListNode(const T& data):_data(data), _prev(NULL), _next(NULL){}};template<class T,class Ref,class Ptr>struct _ListIterator//正向迭代器{typedef ListNode<T> Node;typedef _ListIterator<T, Ref, Ptr> Self;typedef Ref Refrence;typedef Ptr Pointer;_ListIterator(Node* x):_node(x){}Ref& operator*(){return _node->_data;}Ptr operator->(){return &(operstor*())}Self& operator++(){_node = _node->_next;return *this;}Self operator++(int){Self tmp(*this);_node = _node->_next;return tmp;}Self& operator--(){_node = _node->_prev;return *this;}Self operator--(int){Self tmp(*this);_node = _node->_prev;return tmp;}bool operator !=(const Self& s){return _node != s._node;}bool operator ==(const Self& s){return _node == s._node;}Node* _node;};template<class T>class List{typedef ListNode<T> Node;public:typedef _ListIterator<T, T&, T*>Iterator;typedef _ListIterator<T, const T&, const T*>constIterator;Node* BuyNode(const T& x)//构造新节点{return new Node(x);}List()//带头节点的双向链表{_head = BuyNode(T());_head->_next = _head;_head->_prev = _head;}void Clear(){Iterator it = Begin();if (it != End()){Node* del = it._node;++it;delete del;}_head->_next = _head;_head->_prev = _head;}~List(){Clear();delete _head;_head = NULL;}Iterator Begin(){return Iterator(_head->_next);}Iterator End(){return Iterator(_head);}Iterator Begin() const{return constIterator(_head->_next);}Iterator End() const{return constIterator(_head);}Iterator Find(const T& x){Iterator it = Begin();while (it != End()){if (*it == x){return it;}else{++it;}}return End();}void Insert(Iterator& pos, const T& x){assert(pos._node);Node* tmp = BuyNode(x);Node* cur = pos._node;Node* prev = cur->_prev;prev->_next = tmp;tmp->_next = cur;cur->_prev = tmp;tmp->_prev = prev;}Iterator Erase(Iterator pos){assert(!Empty()&&pos._node);Node* cur = pos._node;Node* prev = cur->_prev;Node* next = cur->_next;delete cur;prev->_next = next;next->_prev = prev;return next;//返回下一个位置}bool Empty()//判断链表是否为空{return _head == _head->_next;}void PushBack(const T& x){Insert(End(), x);}void PopBack(){Erase(--End());}void PushFront(const T& x){Insert(Begin(), x);}void PopFront(){Erase(Begin());}void Assign(size_t n, const T& val){Clear();for (size_t i = 0; i < n; ++i){PushBack(val);}}template <class InputIterator>void Assign(InputIterator first, InputIterator last){Clear();while (first != last){PushBack(*first);++first;}}private:Node* _head;Node* _prev;Node* _next;};void Print(List<int>& l)//封装打印函数{List<int>::Iterator it = l.Begin();while (it != l.End()){cout << *it << " ";++it;}cout << endl;}
void  TestList()//测试代码{List<int> l;l.PushBack(1);l.PushBack(2);l.PushBack(3);l.PushBack(4);Print(l);//l.PopBack();//l.PopBack();//l.PushFront(9);//l.PushFront(8);//l.PopFront();List<int>::Iterator it1 = l.Begin();while (it1 != l.End()){if (*it1 % 2 == 0){it1 = l.Erase(it1);}else{++it1;}cout << endl;}Print(l);List<int> l1;l1.Assign(l.Begin(), l.End());Print(l1);}