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PERMUT1 - Permutations |
Let A = [a1, a2, ... an] be a permutation of integers 1, 2, ... n. A pair of indices (i, j), 1 <= i <= j <= n, is an inversion of the permutation A if ai > aj. We are given integers n > 0 and k >= 0. What is the number of n-element permutations containing exactly k inversions?
For instance, the number of 4-element permutations with exactly 1 inversion equals 3.
Task
Write a program which for each data set from a sequence of several data sets:
- reads integers n and k from input,
- computes the number of n-element permutations with exactly k inversions,
- writes the result to output.
Input
The first line of the input file contains one integer d, 1 <= d <= 10, which is the number of data sets. The data sets follow. Each data set occupies one line of the input file and contains two integers n (1 <= n <= 12) and k (0 <= k <= 98) separated by a single space.
Output
The i-th line of the output file should contain one integer - the number of n-element permutations with exactly k inversions.
Example
Input: 1 4 1 Output: 3
Added by: | adrian |
Date: | 2004-06-22 |
Time limit: | 3s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All |
Resource: | III Polish Collegiate Team Programming Contest (AMPPZ), 1998 |
hide comments
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2016-03-08 15:38:29 poojan
Great Problem !Ac 1 go! Another DP for beginners! Great Feeling after solve This! |
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2015-11-08 16:58:42
Input constraints are not valid. Dont assume n can be maximum 12 |
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2015-07-10 15:37:51 xxbloodysantaxx
Don't make a mistake of dividing into two lengths and count there inversions seperately! It will miss out the cases of crossing inversions! Morover it is highly inefficient than the actual solution |
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2015-06-09 12:44:44 PRIBAN91
Nice problem! |
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2014-12-17 17:09:20 sobriquet
Good one. |
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2014-09-08 15:19:52 shankar
WOW an easy one |
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2014-08-15 11:35:06 Garima
Make sure your answer for 1 0 is 1. |
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2014-06-27 22:48:00 ankg
Yo! First Dp! It's awesome! :D |
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2014-06-26 21:06:45 tapopadma
VERY EG ! :) |
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2014-06-02 06:16:41 nitesh kumar
nic 1. |