迭代器失效:
1 如果失效就不能再使用这个迭代器
2 如果使用了,结果是未定义的
insert 和 erase 以后迭代器都失效了, 不能再访问
代码:
#include <iostream>
#include<vector>
#include <algorithm>
#include <assert.h>
using namespace std;
namespace xcj
{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){}//拷贝构造vector(const vector<T>& v):_start(nullptr), _finish(nullptr), _endofstorage(nullptr){reserve(v.capacity());for (auto& e : v){push_back(e);}}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> tmp){swap(tmp);return *this;}~vector(){delete[] _start;_finish = _endofstorage = nullptr;}void reserve(size_t n){if (n > capacity()){T* tmp = new T[n];size_t sz = size();if (_start){//要进行深拷贝时会报错//memcpy(tmp, _start, sizeof(T) * sz);for (size_t i = 0; i < sz; i++){tmp[i] = _start[i];}delete[] _start;}_start = tmp;_finish = _start + sz;_endofstorage = _start + n;}}void reszie(size_t n,const T& val=T()){if (n <= size()){_finish = _start + n;}else{reserve(n);while (_finish < _start + n){*_finish = val;++_finish;}}}void push_back(const T& x){if (_finish == _endofstorage){reserve(capacity() == 0 ? 4 : capacity() * 2);}* _finish = x;++_finish;}void insert(iterator pos, const T& x){assert(pos >= _start);assert(pos <= _finish);if (_finish == _endofstorage){size_t len = pos - _start;reserve(capacity() == 0 ? 4 : capacity() * 2);pos = _start + len;}iterator end = _finish-1;while (end >= pos){*(end + 1) = *end;--end;}*pos = x;++_finish;}iterator erase(iterator pos){assert(pos >= _start);assert(pos <= _finish);iterator it = pos + 1;while (it < _finish){*(it - 1) = *it;++it;}--_finish;return pos;}T& operator[](size_t pos){assert(pos < size());return _start[pos];}const T& operator[](size_t pos) const{assert(pos < size());return _start[pos];}size_t capacity()const{return _endofstorage - _start;}size_t size()const{return _finish - _start;}private:iterator _start;iterator _finish;iterator _endofstorage;};
