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# How To write insertion sort in complete recursive way

Greenhorn
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This is the code for insertion sort, but how am i suppose to make it recursive completely, like not using a single for or while loop,

to be more precise i am stuck at
I am not understanding how am i suppose to make it recursilvely it would be great if someone can do it for me.

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For instance:

You can invoke this method assuming the preceding elements are sorted. I did that with an extra insertionSortHelper method.

Rakibul Mahin
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Piet Souris wrote:For instance:

You can invoke this method assuming the preceding elements are sorted. I did that with an extra insertionSortHelper method.

So should I replace the while loop part and use this code of yours??

Piet Souris
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Yes

Rakibul Mahin
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Piet Souris wrote:Yes

but where did you find the swap function?

Piet Souris
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Made it myself to make the code look a little cleaner

Rakibul Mahin
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Piet Souris wrote:Made it myself to make the code look a little cleaner

but what does this swap method do?

Can you kindly solve the full recursive method and give it to me, it would be very kind of you.

Piet Souris
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If you have an array, then 'void swap(array, i, j)' swaps the elements i and j. If you look at your while loop in your opening post, you do in fact the same. I leave it up to you to implement it (its very easy).

As I said, I have a helper method:

That method returns immediately if i == 0. Otherwise, it calls insertionsortHelper(array, i - 1) and then calls 'getElementIinItsCorrectPlace(arr, i).

Finally, my 'public static insertionsort(int[] array)' method calls insertionsortHelper. Can you figure out what the arguments to use?

Marshal
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Another thing Piet is showing you is how to divide large methods into several small methods.

Rakibul Mahin
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Rakibul Mahin wrote:

Piet Souris wrote:For instance:

You can invoke this method assuming the preceding elements are sorted. I did that with an extra insertionSortHelper method.

So should I replace the while loop part and use this code of yours??

I have almost understood can you tell me what does this i means ?

Piet Souris
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The 'i' means the index, not the vale i. A better name would have been 'index' instead of i.

Rakibul Mahin
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Piet Souris wrote:The 'i' means the index, not the vale i. A better name would have been 'index' instead of i.

Thanks a lot man I have solved it.

Piet Souris
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Yes. And well done!

Two remarks:

1) is the parameter 'last' really necessary?

2) suppose there is a way to get rid of that parameter, then you have the method:

That means that a user, wishing to recurInsertionSort his array, needs to invoke that method, having to specify a value for 'minPos'. Now, that is something you don't want the user to saddle up with. Can you make it so that the user only needs to invoke:

?

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