C++ 的Vector类的简单实现

向右看齐 2021-09-19 05:28 322阅读 0赞

**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