Can someone explain how to append an element to an array in C programming?

问题

If I want to append a number to an array initialized to int, how can I do that?

int arr[10] = {0, 5, 3, 64};
arr[] += 5; //Is this it?, it's not working for me...

I want {0,5, 3, 64, 5} in the end.

I'm used to Python, and in Python there is a function called list.append that appends an element to the list automatically for you. Does such function exist in C?

回答1:

int arr[10] = {0, 5, 3, 64};
arr[4] = 5;

EDIT: So I was asked to explain what's happening when you do:

int arr[10] = {0, 5, 3, 64};

you create an array with 10 elements and you allocate values for the first 4 elements of the array.

Also keep in mind that arr starts at index arr[0] and ends at index arr[9] - 10 elements

arr[0] has value 0;
arr[1] has value 5;
arr[2] has value 3;
arr[3] has value 64;

after that the array contains garbage values / zeroes because you didn't allocated any other values

But you could still allocate 6 more values so when you do

arr[4] = 5;

you allocate the value 5 to the fifth element of the array.

You could do this until you allocate values for the last index of the arr that is arr[9];

Sorry if my explanation is choppy, but I have never been good at explaining things.

回答2:

You can have a counter (freePosition), which will track the next free place in an array of size n.

回答3:

There are only two ways to put a value into an array, and one is just syntactic sugar for the other:

a[i] = v;
*(a+i) = v;

Thus, to put something as the 4th element, you don't have any choice but arr[4] = 5. ~~However, it should fail in your code, because the array is only allocated for 4 elements.~~

回答4:

If you have a code like int arr[10] = {0, 5, 3, 64}; , and you want to append or add a value to next index, you can simply add it by typing a[5] = 5.

The main advantage of doing it like this is you can add or append a value to an any index not required to be continued one, like if I want to append the value 8 to index 9, I can do it by the above concept prior to filling up before indices. But in python by using list.append() you can do it by continued indices.

来源：https://stackoverflow.com/questions/26208788/can-someone-explain-how-to-append-an-element-to-an-array-in-c-programming

标签

arrays

integer

append