弃土取决于阵列被声明的方式是什么？

Question

下面的代码似乎当数组声明如下

int numbers[3] 

工作但是当我尝试宣告它像

int* numbers = new int[3]; 

调整调整大小排列的前两个数字之后似乎迷路。 我真的不能弄清楚是什么betwean两个声明的区别。任何澄清将是有益的。

int main() { 
    int numbers_size = 0; 
    int numbers_capacity = 3; 
    //works when declared like this 
    //does not work when declared like int* numbers = new int[3] 
    int numbers[3]; 
    do { 
    ... 
    if(numbers_capacity == numbers_size) 
     numbers_capacity = resize_array(numbers, numbers_size); 
    }while(numbers[numbers_size - 1] != 0); 
    return 0; 
} 

int resize_array(int* arr, int arr_size) { 
    int* temp = new int[arr_size]; 
    for(int i = 0; i < arr_size; i++) 
    temp[i] = arr[i]; 
    delete [] arr; 
    arr = new int[4*arr_size]; 
    for(int i = 0; i < arr_size; i++) { 
    arr[i] = temp[i]; 
    } 
    delete [] temp; 
    return 4*arr_size; 
} 

Answer 1

你正在改变的arr值在resize_array指向新的存储位置，但调用函数仍然有旧，现在晃来晃去，内存位置。

更改功能：

int* resize_array(int* arr, int arr_size) 
{ 
    int* temp = new int[arr_size]; 
    for(int i = 0; i < arr_size; i++) 
     temp[i] = arr[i]; 

    delete [] arr; // This makes pointer in the calling function 
        // point to deleted memory. 

    arr = new int[4*arr_size]; 
    for(int i = 0; i < arr_size; i++) { 
     arr[i] = temp[i]; 
    } 
    delete [] temp; 

    // Return the newly allocated memory. 
    return arr; 
} 

，并用它喜欢：

numbers_capacity = numbers_size*4; // This is bad. It assumes that 
            // that you are increasing the size by 4 times. 

numbers = resize_array(numbers, numbers_size); 

您可以简单地用一个std::vector<int>，避免所有的头痛。