Remove Duplicate Elements from Unsorted Array - Java Code

Write a java program to remove duplicate elements from an unsorted array. In this tutorial, I have explained three approaches to solve this problem.
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[@sureshnaidu3519]

Very nice approach and explained very well. Subscribed. Thank you

[@ProgrammingTutorials1M]

Thank you.

[@chrisw9597]

These videos are a godsend. I don't normally comment, but you deserve my appraisal. Thank you!

[@ProgrammingTutorials1M]

Thank you Christopher.

[@jeetamitshah6194]

In the first approach, what about the remaining 2 positions in the array? You left them empty. The original array is of length 7 and new array with only unique elements has a length of 5, so what about the remaining 2 positions in the array? Java doesn't allow dynamic arrays so the length of the array is not changing .

[@RajeevKumar-gk1qo]

Explained very well. You are great.

[@ProgrammingTutorials1M]

Thanks a lot

[@ranadheersannihith2362]

In the first approach, every time the last element is getting added arr[j++]=arr[len-1], then if the last element is 5 and not 6 then 5 will again be added at the end and the output could be 1,2,4,5,5.

[@ProgrammingTutorials1M]

Hi Ranadheer, You missed that condition
if (arr[i] != arr[i + 1]) {
arr[j++] = arr[i];
}
In this condition, Second last element is already compared with last element. So, in that case second last element won't be added. You can run the code and check the output.

[@ranadheersannihith2362]

@@ProgrammingTutorials1M I am not talking about second last. Consider 5 as the last element and there is no 6. Then last element 5 has to be added to our output and our output would be 1,2,4,5 and 5.

[@bharathkoneru4008]

@@ranadheersannihith2362 no man, you got it wrong.
arr = {1,2,4,4,5,5,5}
5 ! =5 is not satisfied till last element, so 5 will not be added to the array on iteration using for loop.
{1,2,4}
5 only gets added when we add manually last element of array.
arr = {1,2,4,5}

[@maheshkumarb7729]

Hi All,
I tried for this input -> int[] arr = {4,2,1,5,5,6,7,8,8,9};
Its removing the duplicate values but was not printing the last value i.e., 9 in this example.
We need to use --> for (int i=0; i for (int i=0; i

[@marcos.a8814]

Thank you so much!! for hashing and set the -1 must be removed, only keep it for the first code, which is great because I don't really understand why it needs to be -1

[@SaiTeja-ym2er]

Very Good explanation.Thanks

[@ProgrammingTutorials1M]

You are welcome

[@Rahul39920]

With this approach the problem is with line no: 74. This will throw ArrayIndexOutOfBoundsException when the size of the array is 0. And it adds extra burden to handle last element of Array. We can certainly improve this.

[@shreyaroy4773]

Awesome approach sir! Searched a lot then found this video! Can you please say how to implement the 2nd and 3rd approaches in C++?

[@ProgrammingTutorials1M]

Hi Shreya, I know only java.

[@shreyaroy4773]

@@ProgrammingTutorials1M ok sir! Thank you!

[@sakhi_dikshit]

Thank you so much😇😇 please upload more videos 🙏

[@ProgrammingTutorials1M]

I will try my best

[@explorelife2418]

The code is amazing. Thank you so much. Subscribed 😊😊
Can you please tell how to find the non repeating elements in the array? i.e the elements which occur only once.

[@ProgrammingTutorials1M]

Thanks for your comment. Here is the video link : th-cam.com/video/vx_snk6RQl0/w-d-xo.html

[@7smessi803]

Awesome approch brother'❤️❤️❤️

[@ProgrammingTutorials1M]

Thanks ✌️

[@ProgrammingTutorials1M]

Code link is present in the description box

[@swapniljadhav5461]

Good approaches. Is it possible to remove duplicates from unsorted array without using any collection. For example in O(1) or O(log n) space complexity

[@ProgrammingTutorials1M]

Hi Swapnil, O(1) and O(logn) might not be possible for unsorted array. You need to traverse complete array to figure out the duplicates.

[@sakhi_dikshit]

Please make video on hackerrank problems.

[@mohdamirquadri5796]

Sir instead of void in method use type and return value beacause in every interview there ask this pattern ..

[@ProgrammingTutorials1M]

Yes, In my new videos i have implemented this approach. You can check it.

[@sivaram9439]

is first method is exactly crt for all the testcases....???

[@ProgrammingTutorials1M]

Yes

[@V.LaxmanaVyaas]

Sir the output is in ordered one..not in unordered one sir

[@UnprivilegedDelhi]

what if we need to maintain the order of the array, how can we implement it without sorting the array?

[@ProgrammingTutorials1M]

You can do it by using set data structure.

[@venkyvenky4261]

But output is not in order
You changed the order sir

[@abdulrahmanabdullahi1875]

Why is the sorting important when trying to remove the duplicates from an array?

[@debayanroy6325]

If you use LinkedHashSet instead of HashSet you can even retain the order.

[@Baby_Boy_Mintu]

Thanks sir

[@ProgrammingTutorials1M]

Welcome

[@asifbasheerkhan2855]

we should you linkedhashset instead of simple hashset because order in not preserved .

[@ProgrammingTutorials1M]

If you want to preserve order then you can

[@ArunKumar-ko8po]

thank you :)

[@ProgrammingTutorials1M]

You're welcome!

[@bryanlozano8905]

Can you use merge sort, and eject duplicates during merge routine? Or would all of those repeated shifts hurt the algorithm? I guess you can at least record the index of elements that are to be ejected during sorting.

[@ProgrammingTutorials1M]

But in this case the time complexity would be O(nlogn). There is a tradeoff between time and space here. Using extra space we can solve this problem in linear time.

[@shubhambhosale8467]

make an empty set and insert all array value in that set it get sorted+remove duplicate as well
thanks me later

[@reefmansour3630]

Thaaaaaaannnnnk you the j++ is a smart move !!! thanks

[@ProgrammingTutorials1M]

Please like and share with your friends.

[@Tangoez]

Shabbaruoureyyyy shabana pureyyyy Heyyyyyyy shaburshaburaaa pureyyyyyyy

[@alokkachhap4171]

-> what it is

[@ProgrammingTutorials1M]

This is the lambda expression which is introduced in java 8.

[@jhoanmateofrancovargas1405]

gracias por el vídeo,fue fácil entenderte aunque no hablaras mi idioma xd

[@ProgrammingTutorials1M]

muchas gracias