c++ - 改变数组

Question

我在处理没有 vector 的数组时做了很多不同的事情，我想知道是否有人可以帮助我移动数组中的元素并扩展数组，同时用元素初始化新空间。我觉得我已经非常接近完成这段代码了，但是我遇到了障碍。

#include <iostream>
using namespace std;


// Function prototypes
int *reverse(int *, int);
int *expand(int *, int); 
int *shift(int *, int); 
void display(int[], int);
void display2(int[], int);
void display3(int[], int);


int main()
{
    int const SIZE = 5;
    int myArray [SIZE] = {1, 2, 3, 4, 5};
    int myArray2 [SIZE] = {1, 2, 3, 4, 5};
    int myArray3 [SIZE] = {1, 2, 3, 4, 5};

    int *arraPtr;
    int *arraPtr2;
    int *arraPtr3;

    arraPtr = reverse(myArray, SIZE);

    display(myArray, SIZE);

    arraPtr2 = expand(myArray2, SIZE);

    display2(myArray2, SIZE);

    arraPtr3 = shift(myArray3, SIZE);

    display3(myArray3, SIZE);

    delete [] arraPtr;
    delete [] arraPtr2;
    delete [] arraPtr3;


    return 0;
}



int *reverse(int *arr, int size)
{
    int *copyArray;
    int posChange;

    if( size < 0)
        return NULL;

    copyArray = new int[size];

    for (int index = 0; index < --size; index++)
    {
            posChange = arr[index];
            arr[index] = arr[size];
            arr[size] = posChange;

    }
    return copyArray;

}


int *expand(int *arr, int size)
{
    int *newArray;

        newArray = new int[size * 2];
memcpy( newArray, arr, size * sizeof(int));
for (int index = size; index < (size*2); index++)
    newArray[index] = 0;
return newArray;




}

int *shift(int *arr, int size)
{
    int *newArray;
    newArray = arr;
    newArray = new int [size + 1];
    for (int index = 5; index > 0; index--)
        newArray[index] = newArray[index - 1];

return newArray;


}

void display(int arr[], int size)
{
    for (int index = 0; index < size; index++)
    {
        cout << arr[index] << " ";
    }

        cout << endl;
}

void display2(int arr[], int size)
{
    for (int index = 0; index < size; index++)
    {
        cout << arr[index] << "  ";
    }
        cout << endl;

}

void display3(int arr[], int size)
{
    for (int index = 0; index < size; index++)
    {
        cout <<arr[index] << "  ";
    }
        cout << endl;

}

Answer 1

只有两个编译错误:int newArray;应该是 int* newArray;和 #include <cstring>缺少(memcpy() 所必需的)

此外，行 display(myArray, SIZE);可能是 display(arraPtr, SIZE);同样display2(myArray2, SIZE); -- 否则你只会显示原始数组，而不是函数调用的结果。

但是，这可以受益于更安全和更通用的 C++ 算法，std::copy()和 std::reverse_copy()至少:

int *reverse(int *arr, int size)
{
    int *copyArray = new int[size];
    std::reverse_copy(arr, arr+size, copyArray);
    return copyArray;
}
int *expand(int *arr, int size)
{
    int *newArray = new int[size * 2]();
    std::copy(arr, arr+size, newArray);
    return newArray;
}
int *shift(int *arr, int size)
{
    int* newArray = new int [size + 1]();
    std::copy(arr, arr+size, newArray+1);
    return newArray;
}

完整程序:https://ideone.com/RNFiV