标签：c/c++
/* C++顺序表模板练习 以及 剖析易出现的浅拷贝问题 */
#define _CRT_SECURE_NO_WARNINGS 1
#include <iostream>
#include <string>
using namespace std;
template <typename T>
class SeqList
{
public:
SeqList();
SeqList(const SeqList& s);
~SeqList();
void PushBack(const T& d);
void PopBack();
void PushFront(const T& d);
void PopFront();
int Find(const T& d);
void Reverse();
void Insert(int pos, const T& d);
void sort();
SeqList& operator=(const SeqList& s);
void Print()
{
int i = 0;
for(i = 0; i < _size; i++)
{
cout<<_data[i]<<" ";
}
cout<<endl;
}
private:
void _check_capacity()
{
if(_size == _capacity)
{
T* tmp = new T[2 * _capacity + 3];
//======注意 1 memcpy()浅拷贝问题 ===================
//对于含有指向动态开辟空间的类
//memcpy() 会出现浅拷贝现象 导致两个类的成员指针
//指向同一块空间 析构两次时导致【程序崩溃】
//比如 string类 内部含有这样一个指针
//当然 还有初始预留的空间 如果字符串没有超过预留空间
//指向动态空间的指针为空 用memcpy(）也没事
//但当这个指针指向空间是 一等会由于浅拷贝导致析构
//失败的
//==============================================
string类 结构示意图
// memcpy(tmp, _data, _size * sizeof(T));
//===========================================
//解决方法
//利用 string类 自带的operator=()一个一个复制
//避免出现浅拷贝现象
//不过memcpy()也有优点 那就是效率高
//===========================================
for(int i = 0; i < _size; i++)
{
tmp[i] = _data[i];
}
delete[] _data;
_data = tmp;
_capacity = 2 * _capacity + 3;
}
}
private:
int _size;
int _capacity;
T* _data;
};
//=================注意2 默认拷贝函数出现浅拷贝问题 ===========
//这要写 拷贝构造 防止出现浅拷贝问题
// 例如对于string这种含有指向动态开辟空间 的 指针成员
template <typename T>
SeqList<T>::SeqList(const SeqList<T>& s)
{
_data = new T[s._size];
int i = 0;
for(i = 0; i < s._size; i++)
{
_data[i] = _data[i];
}
_size = s._size;
_capacity = _size;
}
template <typename T>
SeqList<T>::SeqList()
:_size(0)
,_capacity(3)
,_data(new T[_capacity])//注意：声明类变量时要先声明_capacity 再生命_data
{
//cout<<typeid(_capacity).name() <<endl;
//cout<<"SeqList()"<<endl;
}
template <typename T>
SeqList<T>::~SeqList()
{
if (_data != NULL)
{
delete[] _data;
_data = NULL;
}
}
template <typename T>
void SeqList<T>::PushBack(const T& d)
{
_check_capacity();
_data[_size] = d;
_size++;
}
template <typename T>
void SeqList<T>::PopBack()
{
if(_size > 0)
{
_size--;
}
}
template <typename T>
void SeqList<T>::PushFront(const T& d)
{
_check_capacity();
int i = _size;
while(i)
{
_data[i] = _data[i - 1];
i--;
}
_data[0] = d;
_size++;
}
template <typename T>
void SeqList<T>::PopFront()
{
int i = 0;
for(i = 0; i < _size - 1; i++)
{
_data[i] = _data[i + 1];
}
_size--;
}
template <typename T>
SeqList<T>& SeqList<T>::operator=(const SeqList& s)//注意用SeqList<T>&
{
if(this != &s)
{
delete[] _data;
_data = new T[s._capacity];
memcpy(_data, s._data, s._size * sizeof(T));
_size = s._size;
_capacity = s._capacity;
}
return *this;
}
template <typename T>
int SeqList<T>::Find(const T& d)
{
int i = 0;
for (i = 0; i < _size; i++)
{
if(_data[i] == d)
{
return i;
}
}
return -1;
}
template <typename T>
void SeqList<T>::Reverse()
{
int left = 0;
int right = _size - 1;
while(left < right)
{
swap(_data[left], _data[right]);
left++;
right--;
}
}
template <typename T>
void SeqList<T>::Insert(int pos, const T& d)
{
if(pos < 0 || pos > _size)
{
return;
}
_check_capacity();
int i = _size;
_size++;
while(i > pos)
{
_data[i] = _data[i - 1];
i--;
}
_data[pos] = d;
}
template <typename T>
void SeqList<T>::sort()
{
int i = 0;
for(i = 0; i < _size; i++)
{
bool flag = true;
for(int j = 0; j < _size - i - 1; j++)
{
if(_data[j] > _data[j + 1])
{
T temp = _data[j];
_data[j] = _data[j + 1];
_data[j + 1] = temp;
flag = false;
}
}
if(flag)
{
return;
}
}
}
int main()
{
{
//SeqList<int> s1;
/*s1.PushBack(1);
s1.PushBack(2);
s1.PushBack(3);
s1.PushBack(4);
s1.Print();
s1.PopBack();
s1.Print();
s1.PopBack();
s1.Print();
s1.PopBack();
s1.Print();
s1.PopBack();
s1.Print();
s1.PopBack();
s1.Print();
s1.PopBack();
s1.Print();*/
//s1.PushFront(1);
//s1.PushFront(2);
//s1.PushFront(3);
//s1.PushFront(4);
//s1.Print();
//s1.PopFront();
//s1.Print();
//s1.PopFront();
//s1.Print();
//s1.PopFront();
//s1.Print();
//s1.PopFront();
//s1.Print();
//s1.PopFront();
//s1.Print();
//s1.PopFront();
//s1.Print();
/*SeqList<string> s2;
s2.PushBack("1");
s2.PushBack("11111112222222222");
s2.Print();*/
//s2.PushBack();
//s2.PushBack();
//s2.PushBack();
SeqList <string> s1;
s1.PushBack("11111");
s1.PushBack("222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222");
s1.PushBack("33333");
s1.PushBack("44444");
s1.PushBack("44444");
/*s1.PushBack("44444");
s1.PushBack("44444");
s1.PushBack("44444");
s1.PushBack("44444");
s1.PushBack("44444");
s1.PushBack("44444");*/
s1.Print();
SeqList <string> s2(s1);
//s2 = s1;
s2.Print();
/*s1.PushBack(4);
s1.PushBack(3);
s1.PushBack(2);
s1.PushBack(1);
s1.Print();*/
/*s1.sort();
s1.Print();
cout<<s1.Find(3)<<endl;
s1.Insert(s1.Find(3),4);
s1.Print();*/
/*SeqList<int> s2 = s1;
s2.Print();*/
}
//test2();
getchar();
return 0;
}
本文出自 “城市猎人” 博客，请务必保留此出处http://alick.blog.51cto.com/10786574/1754506
标签：c/c++
原文地址：http://alick.blog.51cto.com/10786574/1754506
