_amit.nehra_'s blog

By _amit.nehra_, history, 3 months ago, In English

There are N numbers(1 to N), arranged in increasing order. There are q operation that has to be performed on permutation. In ith operation, we'll have Li, Ri(two indices) and we have to reverse the permutation from arr[Li] to arr[Ri]. At last, after performing all operations, we have to return value at kth position.

N<=10^9
q<=10^5
1<= Li, Ri <=N
k<=N

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3 months ago, # |
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Auto comment: topic has been updated by _amit.nehra_ (previous revision, new revision, compare).

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3 months ago, # |
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Link to the question?

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    3 months ago, # ^ |
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    It was in Online Assessment of SAP LAB, so I don't have the question itself.

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3 months ago, # |
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I think i have done similar question using Treap data structure.

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3 months ago, # |
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unfortunately I can't help you :_(

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3 months ago, # |
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You can use treap or splay tree.

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3 months ago, # |
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You can use treaps as others have said but since this is from an OA, treap is definitely not the intended solution.

lets say after q queries x is at position k, then doing the q queries again in reverse would take x back to position x since it's a permutation. So what we can do is reverse query array and then find at what index k will be after q queries and this can be done quite easily. that index will be our answer.