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[1600 rated ] why this problem is tagged as greedy ?
By User_NULL, history, 21 month(s) ago, In English

Is there any greedy approach for finding minimum operations required for making a_i to b_i ?

https://mirror.codeforces.com/contest/1633/problem/D

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21 month(s) ago, # |
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This is weird! I think this is because we can know how many operations are needed to get from $$$1$$$ to $$$b_i$$$ greedily.

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    21 month(s) ago, # ^ |
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    can you share your greedy approach ?

    i've been trying but not able to come up with any!!

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      21 month(s) ago, # ^ |
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      We can always choose $$$x = 1$$$ so that when performing $$$a_i = a_i + \lfloor{\frac{a_i}x\rfloor}$$$ is the same as $$$ a_i = 2a_i$$$.

      Let $$$b_i$$$ is the minimum number of the above operation to get from $$$1$$$ to $$$i$$$. Sense $$$i <= 10^3$$$ so we need at most $$$\lceil \log_2{10^3} \rceil$$$ operations, $$$b_i \le 10$$$.

      Update:

      Ops! forget about it, in the last operation we can't increase by all values in the range $$$[1, a_i)$$$. Only some of them are available.

      The editorial provided a DP approach for it, check it out.

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21 month(s) ago, # |
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It tagged greedy because it's a knapsack problem.

By the way, thanks for sharing a great problem to solve.

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    21 month(s) ago, # ^ |
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    But the problem can't be solved greedily. The greedy approach only works with the fractional knapsack (as far as I know).

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21 month(s) ago, # |
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Tags are sometimes wrong.

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