Problem 534. Find best domino orientation

Created by Doug Hull

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Given a list of pairs, find the orientation they should be placed in a line, such that the sum of the absolute values of the differences is zero.

Zero means do not invert, One means invert in the order vector.

list = [1 2
        4 2
        2 3

order = [0 1 1]

yields: [1 2][2 4][3 2]
    or: abs(2-2) + abs(4-3)
    or:        0 + 1
    or: 1

There is a unique solution to this problem where the final score is minimized.

Solve

Solution Stats

570 Solutions
170 Solvers

Last Solution submitted on Feb 06, 2020

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5 Comments

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Jean-Marie Sainthillier on 6 Aug 2012

No unique solution. For me it is the last solution of the permutation matrix.

Doug Hull on 7 Aug 2012

For which test statement is there not a unique solution? We need to fix the test suite if there are two answers of same score.

Jean-Marie Sainthillier on 7 Aug 2012

Sorry, it was a mistake.

Andrew Newell on 9 Jan 2015

The statement of the problem is incorrect: "the sum of the absolute values of the differences is zero." You want the smallest sum, but it isn't necessarily zero.

Raihan Ahmed on 6 Jan 2016

Is there any size constraint on this problem ? My solution is not getting accepted ...

Solution Comments

Solution 550812

2 Comments

2 Comments

Jon on 30 Dec 2014

Best solution without lookup table

Ramoflaple on 7 Jul 2015

Never thought for-loop can be used for a matrix.

Solution 73793

2 Comments

2 Comments

Albert Yam on 10 Apr 2012

Aww.. ran out of memory.

Albert Yam on 10 Apr 2012

%the part of the code i cut out, should work in theory ..

fliplist = fliplr(list);
idx = triu(ones(length(list)),0);
for j = 1:length(idx)
idx2 = unique(perms(idx(j,:)),'rows');
[a b] = size(idx2);
for i = 1 : a
idxi = boolean(idx2(i,:)');
list2 = list;
list2(idxi,:) = fliplist(idxi,:);
list2 = list2';
list2 = list2(:);
dlist = abs(diff(list2));
val2 = sum(dlist(2:2:end));
if val2 < val
val = val2;
orientation = idxi';
end
if val == 0
return
end
end
end

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Problem 534. Find best domino orientation

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Problem 534. Find best domino orientation

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