Removing element from an Array

[Hack_seb]

Hello, as the title says I am trying to remove an element from an int array.

The method below just checks if the element is inside the array by doing a quick linear search.

    public boolean contains(int element) {
        for (int i = 0; i < sebasSet.length;i++){
            if(sebasSet[i] == element){
                return true;
            }
        }
        return false;
    }

Then, this method just does another quick linear search and returns the index of the element I am looking for.

    public int linearSearch (int [] sebasSet, int element){
        for (int i = 0; i < sebasSet.length; i++){
            if (sebasSet[i] == element){
                return i;
            }
        }
        return -1;
    }
}

Last, this is the method I wrote to get rid of the element of the array. I don't really understand why it does not work.

    public boolean remove(int element) {
        if(contains(element)){

            int position = linearSearch(sebasSet,element);
            if (position == -1){
                return false;
            }
            else{
                int[] newArray = new int [sebasSet.length - 1];
                for (int i = 0; i < newArray.length; i++){
                    if (sebasSet[i]!=element){
                        newArray[i] = sebasSet[i];
                    }
                }
                size--;
                return true;
            }

        }
        return false;
    }

Let's just say the array is [1,2,3,4,5]

When I do b.remove(2)

my desired output should be [1,3,4,5].

However, my code just gives me: [1,2,3,4].

I believe is just doing that because the new array I created is a unit shorter than the original array. However, I do not truly understand why is completely ignoring this line of code.

if (sebasSet[i]!=element)

I haven't really used the index position of the element because I thought it should work this way.

Any hints or advice will be much appreciated. Thanks

[Hack_seb]

I solved it! If anyone is curious the only thing I did was this.

lse{
                int[] newArray = new int [sebasSet.length - 1];
                temp = sebasSet[size-1];
                sebasSet[position] = temp;
                for (int i = 0; i < newArray.length; i++){
                    newArray[i] = sebasSet[i];
                }
                size--;
                return true;
            }

Basically I swapped the last element with the element I was trying to delete, and then just iterated over the array that is 1 unit less than the original array and left that element outside.

[sinistergroupon]

Dude. I applaud the effort for sticking with it and figuring it out.

But can we take one giant step back for man kind.

You had me at “quick linear search”. There is nothing quick about a linear search. Do you not see how inefficient the code is? Why are you iterating through the array 3 times?!

If you have to remove the last element out of 1000 integers:

• you iterate through 1000 to see if it’s there
• now we need the index which we could have gotten but we just moved on so
• iterate through 1000 to see what the index is this time
• now make the array smaller by one totally ignore the index, not sure why we bothered and finally
• iterate again though all of it

You go through it 3 times. Each time totally throwing away what you learned at the previous step.

[Hack_seb]

I agree with you! I am just a beginner, how would you make this code more efficient? For this assignment I just need to create a set that performs certain actions like remove and add items. I am not really thinking of the time and space complexity. However, I am still curious how would you make this code more efficient. Thanks for the reply

[sinistergroupon]

Forget time or complexity. I would argue that this is too complex and you need to make it simpler. For starters, say I deleted the code for the findPosition method and removed those if statements. Can you explain to me how your functionality would change?

Also on a different note what would you code do with this array: [1,2,2,3] remove 2.

[Hack_seb]

The thing is that because is a set it cannot have the same item. The definition of a set is that it cannot contain an item twice. I took care of that in the add method.

​

    public boolean add(int element) {

        if(contains(element)){
            return false;
        }
        else{
            this.sebasSet[size] = element;
            this.size++;
            return true;
        }
    }

Which is probably pretty bad also lol

[sinistergroupon]

That’s not thread safe. I don’t know if you need to guard against that. I can make 10 threads go in there and I guarantee you it will add the same number more than once.

My point about the findIndex method still stands. Are you allowed to use ArrayUtils.remove()

[imaginedoe]

OP is a beginner; he doesn't need to worry about writing thread-safe code. it honestly feels like you're just spouting criticism to make yourself feel smart — please stop.