# Terrible edgecase for CHECHOC (Codechef Lunchtime July 2020)

To explain in brief about the question

``````    We had to find the maximum sum of all cells in a matrix of dimensions N x M such that all elements lie in range[0,X] and **sum of two adjacent cells is <=Y**. 1≤N,M≤100 ,1≤X,Y≤10^4
``````

Now ,considering that sum of two adjacent cells never exceeds Y and that all cells have non-negative integers in them it is safe to assume that the value in an individual cell would also be <=Y.

But there is one wicked edgecase case when this assumption fails and that is when both M==1 && N ==1
Now because cell doesn’t have any adjacent cells , the question wants us to assume that it can have a value >=Y

The question had a rather simple solution otherwise but it became rather ambiguous because of that edgecase.

There were many ways in which this could have been avoided such as:

1. Better framed constraints.If the queries are regarding adjacent elements , atleast make sure that the question constraints have adjacent elements at all times ! What are we supposed to assume otherwise? IF the constraints were 2≤X,Y≤10^4 it would have never been a problem.
2. By making an announcement! Like plenty of announcements made on codeforces rounds.
3. Including more diverse cases in sample tests so that the task becomes more clear.

I request the codechef team to look into this topic. And if possible remove that test case from final testing.

3 Likes

I think that is one of the most important thing we need to think in codechefs contest ,right??

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I think it is always advised to look for the edge cases in the problem.

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