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11481 - Arrange the Numbers

Posted: Sat Sep 13, 2008 8:21 pm
need help...!!!
i am stuck since contest time, but i have no ability to solve it myself.

Re: 11481 - Arrange the Numbers

Posted: Sat Sep 13, 2008 9:33 pm
Use inclusion-exclusion principle.

Re: 11481 - Arrange the Numbers

Posted: Sun Sep 14, 2008 4:16 am
Is this DP?

Re: 11481 - Arrange the Numbers

Posted: Sun Sep 14, 2008 6:57 am
Yep, I solved it during the contest using a recurrence relation.

Hint : Think of how to get a recurrence relation to find the number of derangements of n numbers.

Re: 11481 - Arrange the Numbers

Posted: Sun Sep 14, 2008 9:10 am
Robert Gerbicz wrote:Use inclusion-exclusion principle.
Can you explain a little more?
Inclusion and exclusion on what?

Re: 11481 - Arrange the Numbers

Posted: Sun Sep 14, 2008 11:12 pm
on which elements won't move:
first we choose which k elements won't move at first m positions (m choose k)
then we want to count how many there are permutations of n' = n - k elements that all of m' = m - k first elements will move
we use in/out
+ all permutations
- all permutations that have at least two elements that won't move
+ all permutations thath have at least three elements that won't move

and so on

Re: 11481 - Arrange the Numbers

Posted: Thu Sep 18, 2008 5:06 am
I tried to solve this prob but getting WA.Anyone please check the following I/O..
Input:

Code: Select all

``````15
1000 500 200
15 5 3
117 111 6
958 54 54
666 654 55
545 21 12
878 500 465
900 250 150
88 54 12
20 10 8
18 18 18
12 5 4
545 500 1
42 32 12
6 5 4``````
My Output:

Code: Select all

``````corected after AC...
Case 1: 762643459
Case 2: 27967972
Case 3: 998177293
Case 4: 531446229
Case 5: 980126982
Case 6: 648615184
Case 7: 329986694
Case 8: 9598617
Case 9: 920587914
Case 10: 125855874
Case 11: 1
Case 12: 176400
Case 13: 399786634
Case 14: 387022056
Case 15: 5``````

Re: 11481 - Arrange the Numbers

Posted: Thu Sep 18, 2008 8:43 am
Input :

Code: Select all

``````2
1000 500 200
15 5 3
``````
My Ac's output :

Code: Select all

``````Case 1: 762643459
Case 2: 27967972
``````

Re: 11481 - Arrange the Numbers

Posted: Sat Sep 20, 2008 6:14 am
@ srrajesh,
srrajesh wrote:
Robert Gerbicz wrote:Use inclusion-exclusion principle.
Can you explain a little more?
Inclusion and exclusion on what?
http://mathworld.wolfram.com/Derangement.html ("Nicholas Bernoulli also solved the problem using the inclusion-exclusion principle")

Re: 11481 - Arrange the Numbers

Posted: Sun Sep 21, 2008 1:03 pm
thx Ron..
silly mistake in my coding.now i get AC..
i solved it with dp.

Re: 11481 - Arrange the Numbers

Posted: Tue Jun 14, 2011 8:26 pm
Whats wrong with my thinking -

From first m we need to choose k, thats mCk
for remaining m - k positions we can't use the first remaining m - k numbers..
So we fill those positions with from end n - m number.
The way we can do that is (n-m)P(m-k)
Now we have remaining n-m positions and n-m numbers
We can fill that with (n-m)!

So in my thinking the solution to (n,m,k) is simply mCk * (n-m)P(m-k) * (n-m)!

I know I am missing something. Can anyone verify
Thanks