debugger2017's blog

How to solve following problem?
By debugger2017, history, 8 years ago, In English

Given an array, find the number of increasing sub-sequences having GCD=1 Example: A={1, 2, 3} Output: 5 The increasing sub-sequences are {1},{1,2},{1,2,3},{1,3},{2,3} The only approach I can think is to try all the possible sub-sequences and calculate their GCD.

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8 years ago, # |
← Rev. 3   Vote: I like it +21 Vote: I do not like it

UPD: contest is over, if you know how to solve this task, I'd like to know either.

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    8 years ago, # ^ |
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    This problem was earlier discussed in another blog 1-2 weeks back on CF.

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    8 years ago, # ^ |
    ← Rev. 2   Vote: I like it +17 Vote: I do not like it

    Constraints were small, so dpij = number of LIS ending at i with GCD j.

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      8 years ago, # ^ |
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      Things will be more clear with a recurrence.

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        8 years ago, # ^ |
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        for(int i=0;i<n;i++)
{
	for(int j=i-1;j>=0;j--)
	{
	 	if(a[i]>a[j])
		{
	 		for(int k=1;k<=100;k++)
			{
			 	dp[i][gcd(a[i],k)]+=dp[j][k];
			}
		}
	}
}

before this , you must set base values for all i, where dp[i][a[i]]=1;
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