C + + Learning-array pointers/pointers arrays

Although I always know their two differences, but not the name should be called which. Here's the difference.

Pointer Array (array of pointers)

As the name implies: This is the array, the elements inside the arrays are pointers.

int*arr[10];

This is equivalent to int *(a[4]) because * the priority is relatively low, so when there is no parenthesis, it is arr和[10] first combined, into an array, and then the element of this array is an integer pointer.

Initialization

This initialization is to be in the form of an array.

forint010; i++){    a[i] = (int *)malloc5sizeof(int) );}

This is to iterate through each array of elements, to the pointer request space, each pointer to a 5 int -size memory.
This time, you will be able to assign a value.

fori0i10i++){    for (int j = 0; j < 5; j++){        a[i][j] = 0;    }}

At this point, all the elements are assigned a value of 0.

Note: Because each element of the array is a pointer. So you won't get an error when you visit a[0][6] . But the value of the output is undefined and more dangerous.

Array pointer (a pointer to an array)

This means I'm a pointer, and the pointer points to an array.

int (*arr)[10];

Here let *和arr 's combine to be a pointer, this pointer points to a int type of array with 10 elements.

Initialization

For the initialization of this I personally think it is relatively difficult to understand.
The first method of initialization:

inttemp[4][Ten] = {};//Method 1int(*arr) [Ten] = temp;//Correct//Method 2int(*Array)[Ten];Array= temp;//Correct//Method 3int(*array_m) [ One], (*array_n) [9];array_m = temp;//ErrorArray_n = temp;//error//Method 4 for(inti =0; I <4; i++) {arr = &temp[i];//Correctarr++;} Arr-= i;//must subtract I to return to the initial position. 

Here only Method 1, 2, 4 is correct, 3 inside the two will error.

Here's how to focus on method 4. Why do arr++ you receive the next int [10] one directly, because it is a pointer to arr an array, that is int [10] , when it arr++ moves forward 10 of the length of an int's memory.

Summarize

The above is the difference. I usually use only pointer arrays in a two-dimensional array and seldom use array pointers.

Because the pointer array is better understood, but we should pay attention to the boundary problem.

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C + + Learning-array pointers/pointers arrays