从函数c++返回数组时遇到问题

void modifyArray(int* arr, int length) {
    // 对数组进行修改
    for (int i = 0; i < length; i++) {
        arr[i] *= 2;
    }
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int length = sizeof(arr) / sizeof(arr[0]);

    modifyArray(arr, length);

    // 输出修改后的数组
    for (int i = 0; i < length; i++) {
        cout << arr[i] << " ";
    }

    return 0;
}

int* createArray(int length) {
    int* arr = new int[length];

    // 对数组进行初始化
    for (int i = 0; i < length; i++) {
        arr[i] = i + 1;
    }

    return arr;
}

void deleteArray(int* arr) {
    delete[] arr;
}

int main() {
    int length = 5;
    int* arr = createArray(length);

    // 输出数组
    for (int i = 0; i < length; i++) {
        cout << arr[i] << " ";
    }

    deleteArray(arr);

    return 0;
}

#include <vector>

std::vector<int> createArray(int length) {
    std::vector<int> arr(length);

    // 对数组进行初始化
    for (int i = 0; i < length; i++) {
        arr[i] = i + 1;
    }

    return arr;
}

int main() {
    int length = 5;
    std::vector<int> arr = createArray(length);

    // 输出数组
    for (int i = 0; i < length; i++) {
        cout << arr[i] << " ";
    }

    return 0;
}