Comments on: Programming Interview Questions 24: Find Next Higher Number With Same Digits

By: Dilip

Dilip — Wed, 01 Aug 2012 12:43:56 +0000

But you can’t just swap pivot element and pivdx+1 element in all cases.
Say the input is 13621. The pivot is 3. After sorting, it becomes 13126. So in this case we have to swap pivot with 6. The moral is you have to traverse through the list to find out the smallest no, greater than the pivot.
We can do binary search to find swap element.
Correct me if i’m wrong

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By: vaibhav goyal

vaibhav goyal — Tue, 24 Jul 2012 10:43:48 +0000

Hi Arden,
There is a huge flaw, the number n has (log n) digits and hence there are (log n)! permutations O((log n)!) is not equal to O(n log n), infact much less; for example the number take a five digit number, number of permutations possible are only 5! and we can use some other sort like radix sort which here would take much less time.
Thanks

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By: arpita

arpita — Thu, 12 Jul 2012 12:01:49 +0000

really nice algo..thnks a lot

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By: Aravind Prasad

Aravind Prasad — Thu, 12 Jul 2012 05:38:18 +0000

Nice logic .. Well explained ..

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By: Ashot Madatyan

Ashot Madatyan — Mon, 18 Jun 2012 20:41:31 +0000

You could also do a slight modification. As soon as the pivot index is found, sort the array from pividx+1 to the end, and swap the pividx element with the pividx+1.

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By: Varadharajan

Varadharajan — Fri, 11 May 2012 04:30:50 +0000

Thank you…

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By: Arden

Arden — Thu, 10 May 2012 22:35:43 +0000

I mention this case right after the code:
“Note that if the digits of the given number is monotonically increasing from right to left, like 43221 then we won’t perform any operations, which is what we want because this is the highest number obtainable from these digits. There’s no higher number, so we return the given number itself.”

Digits of both 9999 and 10000 are monotonically increasing from right to left.

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By: Sandipan

Sandipan — Wed, 09 May 2012 09:18:30 +0000

Since we are search for right to left for a digit which is less than the letter one.
i.e. arr[i] < arr[i+1]
Here the index goes lesser than 0 – it indicates that it is the greater element – no greater element can be found with same digits.

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By: Varadharajan

Varadharajan — Wed, 09 May 2012 09:03:44 +0000

Hi,
Whatif the numbers like 9999,10000???
Can you please tell me??
Thanks.

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By: Ashot Madatyan

Ashot Madatyan — Sun, 05 Feb 2012 19:57:10 +0000

Terse, comprehensive and exact description of the algorithm. Thanks for that.

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