模拟vector

实现了vector的模板，insert, erase, push_back, iterator

#include<iostream>
#include<string.h>
#include<stdio.h>
#include <stdlib.h>
using namespace std;
template <typename T>
class Vector{
public:
    int length = 0;
    int size = 1;
    T *a = (T*) malloc(sizeof(T));;
    T &operator[](int i){
        return a[i];
    }
    T push_back(T in){
        if(length == size){
            T *b;
            b = (T*) malloc(size*2*sizeof(T));
            for(int i = 0; i < size; i++){
                b[i] = a[i];
            }
            delete(a);
            a = b;
            size *= 2;
        }
        a[length++] = in;
    }
    T* begin(){
        return a;
    }
    T* end(){
        return a+length;
    }
    typedef T* iterator;
    void clear(){
        length = 0;
    }
    int insert(int num, T b){
        if(num >= length) return -1;
        for(int i = length; i >= num; i--){
            a[i] = a[i-1];
        }
        a[num] = b;
        length++;
        return 0;
    }
    int erase(int num){
        if(num > length){
            return -1;
        }
        for(int i = num; i <length-1; i++){
            a[i] = a[i]+1;
        }
        length --;
        return 0;
    }
};
class cl{
public:

    int a, b;
    cl(){a = 0, b = 0;};
};
Vector<int> v;
Vector<cl> c;
int main(){
    cl a;
    c.push_back(a);
    Vector<cl>::iterator It;
    for(It=c.begin();It!=c.end();It++)
        cout<<It->a<<" "<<It->b;
        cout<<endl;

    int *b = (int*) malloc(10);
    printf("%d", b[0]);
    for(int i = 0; i < 10; i++){
        v.push_back(i);
    }
    for(int i = 0; i < 10; i++){
        printf("%d ", v[i]);
    }puts("");
    Vector<int>::iterator it;
    for(it=v.begin();it!=v.end();it++)
        cout<<*it<<" ";
        cout<<endl;
    printf("%d %d\n", v.size, v.length);
    v.insert(0, 1);
    for(it=v.begin();it!=v.end();it++)
        cout<<*it<<" ";
        cout<<endl;
    printf("%d %d\n", v.size, v.length);
    v.erase(2);
    v.erase(3);
    for(it=v.begin();it!=v.end();it++)
        cout<<*it<<" ";
        cout<<endl;
    printf("%d %d\n", v.size, v.length);

}