vector类的简单实现

vector支持很多种数据类型，故要定义成模板类

0、数据成员

• 长度 theSize
• 容量 theCapacity
• 指针 T* array
• 另外还要指定容量的增长步长

	int theSize;
	int theCapacity;
	T* array;
	#define WALK_LENGTH 64;

　　

1、构造函数

• 无参数构造函数
• 用几个相同值初始化的构造函数
• 拷贝构造函数
• 析构函数

        myVector():theSize(0),theCapacity(0),array(NULL){}
	myVector(const T& target , int num):theSize(0),theCapacity(0),array(NULL)
	{
		while( num-- )
			push_back(target);
	}
	myVector(const myVector<T>& other):theSize(0),theCapacity(0),array(NULL)
	{
		// 已重载本类=操作符，有开辟新空间，仍属于深拷贝
		*this = other; //重载=
	}
	~myVector()
	{
		clear();
	}    

　　

2、基本成员函数

• 长度获取
• 容量获取
• 是否为空
• 清空
• 打印

        int size() const
	{
		return theSize;
	}

	int capacity() const
	{
		return theCapacity;
	}

	bool empty()
	{
		return theSize==0;
	}

	void clear()
	{
		if( array )
			delete array;
		array = NULL;
		theSize = 0;
		theCapacity = 0;
	}

	void printArray()
	{
		for( int i=0; i<theSize; i++ )
			cout<<array[i]<<" ";
		cout<<",size="<<theSize<<" ,capacity="<<theCapacity<<endl;
	}

　　

3、实现增删

• 在头插入
• 在尾插入
• 在指定位置插入
• 删除指定位置

	void push_back(const T& target)
	{
		insert_before(theSize, target);
	}

	void push_front(const T& target)
	{
		insert_before(0, target);
	}

	void insert_before(const int& pos, const T& target)
	{
		if(theSize == theCapacity)
		{
			/* array没有delete之前，原来的空间仍然存在，
			/* 当array申请了新空间，只是失去了旧空间的指向，
			/* 用oldarray指向旧空间，等新空间拷贝完，再delete旧空间
			*/
			T* oldarray = array;
			theCapacity += WALK_LENGTH;
			array = new T[theCapacity];
			for( int i=0; i<theSize; i++ )
				array[i] = oldarray[i];
			delete oldarray;
		}

		for( int i=theSize; i>pos; i-- )
			array[i] = array[i-1];
		array[pos] = target;
		theSize++;
	}

	void erase(const int& pos)
	{
		if( pos < theSize )
		{
			for( int i=pos; i<theSize; i++ )
				array[i] = array[i+1];
			theSize--;
		}
	}

　　

4、操作符重载

• 赋值操作符 = 
• 下标操作符  [ ]

	myVector<T>& operator = (const myVector<T>& other)
	{
		//参数other为const 所以other调用的函数都应定义为const
		if( this == &other )
			return *this;
		clear();
		theSize = other.size();
		theCapacity = other.capacity();
		array = new T[theCapacity];
		for( int i=0; i<theSize; i++ )
			array[i] = other[i]; //重载[]
		return *this;
	}

	T& operator [] ( const int& pos ) const
	{
		assert(pos<theSize);
		return array[pos];
	}

　　

总结：整体代码

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

template<typename T>
class myVector
{
private:
	int theSize;
	int theCapacity;
	T* array;
	#define WALK_LENGTH 64;
public:
	myVector():theSize(0),theCapacity(0),array(NULL){}
	myVector(const T& target , int num):theSize(0),theCapacity(0),array(NULL)
	{
		while( num-- )
			push_back(target);
	}
	myVector(const myVector<T>& other):theSize(0),theCapacity(0),array(NULL)
	{
		// 已重载本类=操作符，有开辟新空间，仍属于深拷贝
		*this = other; //重载=
	}
	~myVector()
	{
		clear();
	}

	myVector<T>& operator = (const myVector<T>& other)
	{
		//参数other为const 所以other调用的函数都应定义为const
		if( this == &other )
			return *this;
		clear();
		theSize = other.size();
		theCapacity = other.capacity();
		array = new T[theCapacity];
		for( int i=0; i<theSize; i++ )
			array[i] = other[i]; //重载[]
		return *this;
	}

	T& operator [] ( const int& pos ) const
	{
		assert(pos<theSize);
		return array[pos];
	}

	void clear()
	{
		if( array )
			delete array;
		array = NULL;
		theSize = 0;
		theCapacity = 0;
	}

	int size() const
	{
		return theSize;
	}

	int capacity() const
	{
		return theCapacity;
	}

	bool empty()
	{
		return theSize==0;
	}

	void push_back(const T& target)
	{
		insert_before(theSize, target);
	}

	void push_front(const T& target)
	{
		insert_before(0, target);
	}

	void insert_before(const int& pos, const T& target)
	{
		if(theSize == theCapacity)
		{
			/* array没有delete之前，原来的空间仍然存在，
			/* 当array申请了新空间，只是失去了旧空间的指向，
			/* 用oldarray指向旧空间，等新空间拷贝完，再delete旧空间
			*/
			T* oldarray = array;
			theCapacity += WALK_LENGTH;
			array = new T[theCapacity];
			for( int i=0; i<theSize; i++ )
				array[i] = oldarray[i];
			delete oldarray;
		}

		for( int i=theSize; i>pos; i-- )
			array[i] = array[i-1];
		array[pos] = target;
		theSize++;
	}

	void erase(const int& pos)
	{
		if( pos < theSize )
		{
			for( int i=pos; i<theSize; i++ )
				array[i] = array[i+1];
			theSize--;
		}
	}

	void printArray()
	{
		for( int i=0; i<theSize; i++ )
			cout<<array[i]<<" ";
		cout<<",size="<<theSize<<" ,capacity="<<theCapacity<<endl;
	}
};

int main()
{
	myVector<int> vec1; //无参数构造函数

	cout<<"相同值赋值的构造函数"<<endl;
	myVector<int> vec2(2,4);
	vec2.printArray();

	cout<<"拷贝构造函数"<<endl;
	myVector<int> vec3(vec2);
	vec3.printArray();

	cout<<"在头插入 1"<<endl;
	vec2.push_front(1);
	vec2.printArray();

	cout<<"删除位置11"<<endl;
	vec2.erase(11);
	vec2.printArray();

	cout<<"删除位置0"<<endl;
	vec2.erase(0);
	vec2.printArray();

	cout<<"在尾插入3"<<endl;
	vec2.push_back(3);
	vec2.printArray();

	cout<<"在位置2之前插入4"<<endl;
	vec2.insert_before(2,4);
	vec2.printArray();

	cout<<"操作符=重载"<<endl;
	vec1 = vec2;
	vec1.printArray();

	return 0;
}

　　执行结果：