C++ 的Vector类的简单实现

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一 代码

#include<algorithm>
#include<iostream>
#include <assert.h>
using namespace std;
template<typename T>
class myVector
{
private:
    /*walk length*/
    /*myVector each time increase space length*/
    #define WALK_LENGTH 64;

public:
    /*default constructor*/
    myVector():array(0),theSize(0),theCapacity(0){    }
    myVector(const T& t,unsigned int n):array(0),theSize(0),theCapacity(0){
        while(n--){
            push_back(t);
        }
    }

    /*copy constructor*/
    myVector(const myVector<T>& other):array(0),theSize(0),theCapacity(0){
        *this = other;
    }

    /*= operator*/
    myVector<T>& operator =(myVector<T>& other){
        if(this == &other)
            return *this;
        clear();
        theSize = other.size();
        theCapacity = other.capacity();
        array = new T[theCapacity];
        for(unsigned int i = 0 ;i<theSize;++i)
        {
            array[i] = other[i];
        }
        return *this;
    }

    /*destructor*/
    ~myVector(){
        clear();
    }

    /*the pos must be less than myVector.size();*/
    T& operator[](unsigned int pos){
        assert(pos<theSize);
        return array[pos];
    }

    /*element theSize*/
    unsigned int size(){
        return theSize;
    }

    /*alloc theSize*/
    unsigned int capacity(){
        return theCapacity;
    }
    
    /*is  empty*/
    bool empty(){
        return theSize == 0;
    }

    /*clear myVector*/
    void clear(){
        deallocator(array);
        array = 0;
        theSize = 0;
        theCapacity = 0;
    }

    /*adds an element in the back of myVector*/  
    void push_back(const T& t){
        insert_after(theSize-1,t);
    }

    /*adds an element int the front of myVector*/
    void push_front(const T& t){
        insert_before(0,t);
    }

    /*inserts an element after the pos*/
    /*the pos must be in [0,theSize);*/
    void insert_after(int pos,const T& t){
        insert_before(pos+1,t);
    }

    /*inserts an element before the pos*/
    /*the pos must be less than the myVector.size()*/
    void insert_before(int pos,const T& t){
        if(theSize==theCapacity){
            T* oldArray = array;
            theCapacity += WALK_LENGTH;
            array = allocator(theCapacity);
            /*memcpy(array,oldArray,theSize*sizeof(T)):*/
            for(unsigned int i = 0 ;i<theSize;++i){
                array[i] = oldArray[i];
            }
            deallocator(oldArray);
        }

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

    /*erases an element in the pos;*/
    /*pos must be in [0,theSize);*/
    void erase(unsigned int pos){
        if(pos<theSize){
            --theSize;
            for(unsigned int i = pos;i<theSize;++i){
                array[i] = array[i+1];
            }
        }
    }

private:
    T*  allocator(unsigned int size){
        return new T[size];
    }

    void deallocator(T* arr){
        if(arr)
            delete[] arr;
    }
private:
    T*                array;
    unsigned int    theSize;
    unsigned int    theCapacity;
};

void printfVector(myVector<int>& vector1){
    for(unsigned int i = 0 ; i < vector1.size();++i){
        cout<<vector1[i]<<",";
    }
    cout<<"alloc size = "<<vector1.capacity()<<",size = "<<vector1.size()<<endl;
}

int main(){
    myVector<int> myVector1;
    myVector<int> myVector2(0,10);
    myVector2.push_front(1);
    myVector2.erase(11);
    printfVector(myVector2);
    myVector1.push_back(2);
    myVector1.push_front(1);
    printfVector(myVector1);
    myVector1.insert_after(1,3);
    printfVector(myVector1);

    myVector2 = myVector1;
    myVector2.insert_before(0,0);
    myVector2.insert_before(1,-1);
    printfVector(myVector2);
    return 0;
}

二 运行

[root@localhost charpter03]# g++ 0317.cpp -o 0317
[root@localhost charpter03]# ./0317
1,0,0,0,0,0,0,0,0,0,0,alloc size = 64,size = 11
1,2,alloc size = 64,size = 2
1,2,3,alloc size = 64,size = 3
0,-1,1,2,3,alloc size = 64,size = 5