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Asked: 2026-06-06T15:34:41+00:00

I was trying to solve this problem – http://www.spoj.pl/problems/LISA/ I thought of Greedy initially,

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I was trying to solve this problem – http://www.spoj.pl/problems/LISA/

I thought of Greedy initially, but realized later that it wouldn’t work.
It seems like a DP problem.
I’m not able to form the recurrence relation.
I’m not able to form the recurrence relation. It’s not just this problem, but I get stuck whenever I encounter a slightly difficult DP problem. I know this must be common and practice would help. But I am just moving from one problem to another without actually finding the solution.

Any advise would be great, on the above problem and in general, DP encounters.

Thanks a lot.

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1 Answer

  1. Editorial Team

    Note that operations allowed are only + and * – binary operations that are strictly increasing in regard to both operands (they are positive).

    Let dp[l][r] be the maximum outcome from substring [l,r]

    Here are tips about this problem, which also apply to every dp.

    1) What are base cases? (HINT: something very simple, that doesn’t change its value with adding/removing brackets)

    2) How do you move from bigger problem to smaller problem(s)? (HINT: you can try to find the place of last operation)

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