http://codeforces.net/problemset/problem/414/B
Can anyone help me in understand the problem.Just need explaination.Thanks in advance
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A sequence is called good if all the numbers are divided by its previous number(excluding the first number ofcourse). So a sequence like — 1,4,12,36 is called good but 1,4,8,14 is not good.
Now you will be given n (the maximum number you can use in the sequence) and k (length of sequence). You have to tell how many sequences can be made out of these restrictions.
Let dp[k][cur] be the number of good sequences with k numbers that ends with cur. So —
Recurrence : From a number cur we can move to all the divisors of cur. Say the divisors of cur are — x1, x2, x3, ... xn. Then our recurrence will look like —
Base case : It's easy to tell that base case is for n = 1. (Figure out what you have to do then)
Now you only need to find a good way to store all the divisors of the numbers from 1 to 2000.
You can see my code if you get stuck : 27958781
Thanks brother.