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How to achieve matrix sort in python?

+1 vote
42 views

I have a matrix of numbers representing the nodal points as follows:

Element No. Nodes

1 1 2 3 4
2 5 6 7 8
3 2 3 9 10
...........................
...........................
x 9 10 11 12
...........................

so this is a matrix of numbers 4 x n
Elements 1 and 3 are neighbours (as they share nodes 2 3). Similarly elements 3 and x are neighbours (they share nodes 9 and 10). I want to sort the matrix in such a way all the elements are sequentially arranged.

posted Aug 21, 2013 by Anderson

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1 Answer

+1 vote

I think you want a topological sort algorithm. See here: http://en.wikipedia.org/wiki/Topological_sorting

Before that though you'll want to preprocess your matrix into a data structure that allows you to easily find the elements adjacent to any given element. A list of lists is one approach:

graph = [
 [3], # nodes adjacent to element 1
 [], # element 2
 [1, x], # element 3
 ...
 [3] # element x
]
answer Aug 21, 2013 by Garima Jain
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0 votes

suppose

A(n,m) = 
1 2 3         
4 5 6                            
7 8 9

and 

B(p, q) = 
1 1
1 1

What is best method to find min of square of difference of sub-matrices of A and B e.g.

sub-matrices of A =

1 2    |     2 3   |    4 5    |   5 6
3 4    |     5 6   |    7 8    |   8 9

Difference of first sub-matrix of A with B =

(1-1)  (2-1)    = |     0 1
(3-1)  (4-1)      |     2 3

sum of square of elements = 0*0 + 1*1 + 2*2 + 3*3 = 14

similar steps for other sub-matrices of A

Please suggest looking for an alternate method or algorithm which has time complexity less than O(n*m*p*q)


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