How can i know what's the last position with a value on arrays?

Question

so i have to do a program that should take the value you give and assign it to a position in the array, but how can i know what's the next position avaible? (example: a = {1,2,3,0,0,0,0} the zeros are the avaible positions but how do i get my program to recgonize that? and assign the number i want to that position?) Thanks

Answer 1

Excellent question.

Break down:
* Check if the value of an element in the array is 0.
* If it is, that's the position you add the number into the array.
* If it isn't 0, check the next position.

This is a linear seach.

Here's an example code:

final int NUM = 5;
// the number to add into the array

int[] theArray = {4,0,2,1,0,0};

for(int i = 0; i < theArray.length; i++)
if(theArray[i] == 0)
{
theArray[i] = NUM;
break;
}

// Search the array for an empty space, if it's there, set the value avcordingly and exit the loop

Now the array is:
4,5,2,1,0,0

Answer 2

Yes, it would. That can be a problem.

You could keep track of how many things you've added into the array, leaving the spaces that came before that number the way they are:

int arraySize = 3;
int[] myArray = {0, 6, 3, 0, 0};

final int NUM = 4;
myArray[arraySize++] = NUM;

However, now you will no longer be able to have an array like:
{3, 0, 5, 8, 2, 0}
Where the first 0 is the empty position and the last 0 is just a regular 0 that you want to use.

So, if that's an issue I'd then suggest that you use an arrayList instead of an array.
Or, use some other value like -1 to indicate an empty spot in the array. (And initially fill it with -1's).

Answer 3

xD

Answer 4

Thanks a lot, but what if i wanna assign 0 to a position? wouldn't this code change it for the next number i assign?

Answer 5

Thanks a lot, you really saved my life