[algogeeks] Re: a puzzle

2010-05-08 Thread Afroz Mohiuddin
May not be only rotation, maybe rotation, flipping etc, just a
orthogonal/orthonormal transformation matrix

On Sat, May 8, 2010 at 9:19 AM, Afroz Mohiuddin afrozena...@gmail.comwrote:

 I have a set of n-dimensional vectors, lets say, v1, v2, v3, ... vm

 vi, vj means the dot product of vi and vj.

 It is known that vi, vj = 0 forall i, j  i.e. the angle between any
 two of them is less equal to 90 degrees, which basically means that all of
 them can be occupied in a single quadrant in the n-dimensional space.
 Because in any quadrant, the maximum angle between two vectors both lying
 inside the quadrant is 90 degrees.

 Can you come up with a orthonormal transformation U, such that Uvi = 0 ...
 i.e. an orthonormal transformation (rotation basically, i want the rotation
 matrix U), such that all those vectors come in the positive quadrant.

 There will always exist such a matrix U because all the angles are less
 than 90degrees, can you get a way to find one of them.


 --
 We are here on earth to do good for others. What the others are here for, I
 don't know.

 Afroz Mohiuddin



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[algogeeks] a puzzle

2010-05-08 Thread Afroz Mohiuddin
I have a set of n-dimensional vectors, lets say, v1, v2, v3, ... vm

vi, vj means the dot product of vi and vj.

It is known that vi, vj = 0 forall i, j  i.e. the angle between any
two of them is less equal to 90 degrees, which basically means that all of
them can be occupied in a single quadrant in the n-dimensional space.
Because in any quadrant, the maximum angle between two vectors both lying
inside the quadrant is 90 degrees.

Can you come up with a orthonormal transformation U, such that Uvi = 0 ...
i.e. an orthonormal transformation (rotation basically, i want the rotation
matrix U), such that all those vectors come in the positive quadrant.

There will always exist such a matrix U because all the angles are less than
90degrees, can you get a way to find one of them.


-- 
We are here on earth to do good for others. What the others are here for, I
don't know.

Afroz Mohiuddin
Final Year Masters Student
Dept Computer Science and Engineering
Indian Institute of Technology Kanpur
Kanpur - 208016
INDIA

Address:  F-112 Hall 9
Telephone: [91]9838773891
Email: afrozena...@gmail.com
  a...@iitk.ac.in
  a...@cse.iitk.ac.in

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Re: [algogeeks] question

2010-05-05 Thread Afroz Mohiuddin
Well if you want a sum of exactly 0 (or any constant) , there is an O(N^2)
way

Take your array, and hash it, note that it is always possible to hash a
static set of keys so that the search/find in it is worst case O(1). This
takes O(N) space, and time.

Then over all the tuples of numbers in the original array (a,b) check if 0 -
(a+b) is there in the hash set, time complexity O(N*N).

For closest to 0 I guess the above solution is good.


On Mon, May 3, 2010 at 2:18 PM, jalaj jaiswal jalaj.jaiswa...@gmail.comwrote:


 given an array(unsorted) may contain negative numbers too
 find the index of three numbers whose sum is closest to zero  in  O(N2 log
 N) time and O(N) space.

 P.S -3 is more close to zero then -6 (number line ...)
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 With Regards,
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 +919026283397
 B.TECH IT
 IIIT ALLAHABAD

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We are here on earth to do good for others. What the others are here for, I
don't know.

Afroz Mohiuddin
Final Year Masters Student
Dept Computer Science and Engineering
Indian Institute of Technology Kanpur
Kanpur - 208016
INDIA

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Re: [algogeeks] value of n

2010-05-01 Thread Afroz Mohiuddin
An easy way to do would be to plot both functions in matlab, n and 8log(n)
... just see when y = x is below y = 8log(x) happens between 3= n = 25
if log is to natural base  if it was log base 2 ... 3= n = 43

On Sat, May 1, 2010 at 10:43 AM, Amit Agarwal lifea...@gmail.com wrote:

 I could not get you properly. This is an equation comes from the problem
 statement where I need to find out cut-off value of n between insertion and
 merge sort. I think equation is part of basic mathematics but I don't
 remember how do I solve it.


 -Regards
 Amit Agarwal
 Contact: 09765348182
 www.amitagrwal.com




 On Sat, May 1, 2010 at 9:13 AM, abhijith reddy 
 abhijith200...@gmail.comwrote:

 binary search on n

 On Fri, Apr 30, 2010 at 10:15 PM, Amit Agarwal lifea...@gmail.comwrote:

 how do I compute n from this equation.
 n  8lg(n)

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-- 
We are here on earth to do good for others. What the others are here for, I
don't know.

Afroz Mohiuddin
Final Year Masters Student
Dept Computer Science and Engineering
Indian Institute of Technology Kanpur
Kanpur - 208016
INDIA

Address:  F-112 Hall 9
Telephone: [91]9838773891
Email: afrozena...@gmail.com
  a...@iitk.ac.in
  a...@cse.iitk.ac.in

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Re: [algogeeks] Add 2 long integers with digits represented by linked lists

2010-01-27 Thread Afroz Mohiuddin
The solution is essentially the same as Anurag's; Only that it would be
simple to reverse both the lists
So now the lists look like

Num 1 = 123456
Num 2= 1234
Link-1-Link-2-Link-3-Link-4-Link5-Link6 head_num1
Link-1-Link-2-Link-3-Link-4 -head_num2

Now basically loop, and add the keys, remembering to take the carry ... and
if there is carry in the last stage, then make an extra node.

Regards



On Wed, Jan 27, 2010 at 11:07 AM, Anurag Bhatia abhati...@gmail.com wrote:

 Let us take an example -

 Num 1 = 123456
 Num 2= 1234
 Link-1-Link-2-Link-3-Link-4-Link5-Link6
 Link-1-Link-2-Link-3-Link-4

 Add nodes into linkedlist 1 till either one of the list is not null.
 Make sure you process the carry in each iteration.


 --AB


 On Tue, Jan 26, 2010 at 9:47 PM, Algoose Chase harishp...@gmail.com
 wrote:
  conditions:
  NO extra memory (@ stack or Heap) at all. No recursion.
 
  Any body has got any hint about how to get this done ?
 
 
 
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-- 
We are here on earth to do good for others. What the others are here for, I
don't know.

Afroz Mohiuddin
Final Year Masters Student
Dept Computer Science and Engineering
Indian Institute of Technology Kanpur
Kanpur - 208016
INDIA

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