C++模板类实现顺序表

#pragma once

#include<stdio.h>
#include <iostream>
#include<string>
#include<assert.h>
using namespace std;

template <class T>
class Vector
{
public:
Vector()
: _a(NULL)
, _size(0)
, _capacity(0)
{}

~Vector()
{
if (_a)
{
delete []_a;
_a = NULL;
_capacity = _size = 0;
}
}
void Pushback(const T& x)//尾插
{
_CheckCapacity();

_a[_size] = x;
++_size;
}
void Popback()//尾删
{
if (_size == 0)
{
return;
}
else
{
--_size;
}
}
void PushFront(const T& x)//头插
{
_CheckCapacity();
if (_size == 0)
{
++_size;
_a[0] = x;
}
else
{
for (size_t i = _size; i > 0; i--)
{
_a[i] = _a[i - 1];
}
_a[0] = x;
++_size;
}
}

void PopFront()
{
if (_size == 0)
{
return;
}
else
{
for (size_t i = 0; i < _1size; i++)
{
_a[i] = _a[i + 1];
}
--_size;
}
}
int Find(const T& x)
{
for (size_t i = 0; i < _size; i++)
{
if (_a[i] == x)
{
return i;
}
}
return -1;
}
void insert(size_t pos, const T& x)//在任意位置前面插入一个元素
{
assert((pos >= 0) && (pos < _size));
_CheckCapacity();
for (size_t i = _size; i > pos; i--)
{
_a[i] = _a[i - 1];
}
_a[pos] = x;
_size++;

}

void Erase(size_t pos)
{
assert((pos >= 0) && (pos < _size));
for (size_t i = pos; i < _size; i++)
{
_a[i] = _a[i + 1];
}
--_size;
}
void Print()
{
for (size_t i = 0; i < _size; i++)
{
cout << _a[i] << " ";
}
}
protected:
void _CheckCapacity()
{
if (_size>=_capacity)
{
size_t newCapacity = _capacity * 2 + 3;
T *tmp = new T[newCapacity];//new除了开辟这么多空间，还会调用T的构造函数对其初始化
if (_a)
{
/*memcpy(tmp, _a, sizeof(T)*_size);
delete[] _a;*/
for (size_t i = 0; i < _size; ++i)
{
tmp[i] = _a[i];
}
}
_capacity = newCapacity;
_a = tmp;
}
}
protected:
T *_a;
size_t _size;
size_t _capacity;
};

void TestVector1()
{
Vector<int> V1;
V1.Pushback(1);
V1.Pushback(2);
V1.Pushback(3);
V1.Erase(2);
V1.Print();
}