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Discussion of Problem 1604. Country of Fools

What's your algo?
Posted by ACSpeed 25 Nov 2011 20:46
Can you guys share your approach ( and proof if possible ) because mine, though AC, is not very certain. I rely on greedy approach which output pairs with maximum number and minimum number.

Use sort and find min and max after output each pair.
Quite slow, 0.14s :)
Re: What's your algo?
Posted by gautamvs 27 Mar 2013 12:56
Greedy approach is fine but why output pairs with maximum number and minimum number ??
ACSpeed wrote 25 November 2011 20:46
Can you guys share your approach ( and proof if possible ) because mine, though AC, is not very certain. I rely on greedy approach which output pairs with maximum number and minimum number.

Use sort and find min and max after output each pair.
Quite slow, 0.14s :)
Re: What's your algo?
Posted by Ion Ureche 16 Sep 2013 14:30
I used a max heap in which I hold pairs like, number i (index of the sign) and frequency of that sign. Each time I pop out from that heap the 2 index with maximal frequency, decrement their frequency and update the heap from their indexes.

I was sure that there is a more simplier aproach to that problem(like greedy), without using heap, but I was just 99.9% sure that with heap I will got AC, and so it was. :)


Re: What's your algo?
Posted by B@R5uk 10 Jan 2018 15:41
The same here. I'm using heap, but I'm pulling entries one by one, decrementing and not adding them back until next entry is pulled. I was 146% sure this would work when I decided to implement this algo and it not that bad in terms of time: O(n log k). But I wondered if there is a simple straightforward algo that also would work. Turned out there is.