类中的 C++ 向量

Question

i am working on a worksheet i have for university and the question asks me to "Allow a user to enter 10 numbers from the keyboard into an array" however we have been told that we need to use classes and vectors for this task. When i run my code i get an error stating: "Expression: Vector subscript out of range" can anyone help?

Array.h

#include <iostream>
#include <vector>

using namespace std;

class Array
{
private:
    vector<int> lists;
public:
    void fillArray();
    void printForwards();
    void halfandHalf();
    void shiftArrayRight();

    Array();
    Array(vector<int>);
};

Array.cpp

#include "Array.h"
Array::Array()
{
    lists[10];
}
Array::Array(vector<int> lists)
{
    this->lists = lists;
}
void Array::fillArray()
{
    for (int i = 0; i < 10; i++)
    {
        cin >> lists[i];
    }
}
void Array::printForwards()
{
    for (int i = 0; i < 10; i++)
    {
        cout << lists[i];
    }
}

Source.cpp

#include <iostream>
#include "Array.h"
using namespace std; 

int main()
{

    Array list1,list2;

    //fill array 1 
    list1.fillArray();
    //fill array 2 
    list2.fillArray();

    // print array 1 
    list1.printForwards();
    //print array 2
    list2.printForwards();

    system("pause");
    return 0;
}

Thanks in advance

Answer 1

lists[10]; is not going to create a vector of size 10. It is going to try and access the 11th element of an empty vector. If you wanted to create a vector of size 10 then you can use

Array::Array() : lists(std::vector<int>(10, 0)) {}

I would also suggest you change

Array::Array(vector<int> lists)
{
    this->lists = lists;
}

To

Array::Array(vector<int> lists) lists(lists) {}

You should also change your for loops to use the vector size() instead of a hard coded value

void Array::fillArray()
{
    for (int i = 0; i < lists.size(); i++) // uses size()
    {
        cin >> lists[i];
    }
}
void Array::printForwards()
{
    for (int i = 0; i < lists.size(); i++) // uses size()
    {
        cout << lists[i];
    }
}

Or if you have C++11 or higher you can use a ranged based for loop like

void Array::fillArray()
{
    for (auto& e : lists)
    {
        cin >> e;
    }
}
void Array::printForwards()
{
    for (const auto& e : lists)
    {
        cout << e;
    }
}