Problem 1022. Knot Count - Speed

Created by Richard Zapor

Solve Later

The Matlab Semi-Annual Contest Grand Finale is Knots.

This Challenge is to Speed up the Scoring routine that counts the number of Knots.

Details and examples are at Knots Rules.

Input: [adjacency xy]

adjacency is an NxN matrix of topologically adjacent(connected) points
xy is an Nx2 matrix giving the X and Y coordinates for the N points

Output: nKnots; Number of Knots

Scoring: Speed; Based on cumulative time of Knots [ 3 6 15 18 24 30 37 42 46 49]; Nominal Time 9.7 sec

Baseline Knot Contest Knot scoring for all 50 test cases is 63 seconds on Cody.

Solve

Solution Stats

6 Solutions
2 Solvers

Last Solution submitted on Nov 16, 2013

Last 200 Solutions

Problem Comments

2 Comments

2 Comments

Richard Zapor on 10 Nov 2012

The Knots Contest GradeIt function is not the number of Knots. FYI

Alfonso Nieto-Castanon on 13 Nov 2013

if possible could you fix the url in this problem testsuite? (and perhaps also in the Rubik's series as well? it seems tinyurls tend to have a short life...)

Solution Comments

Solution 352810

2 Comments

2 Comments

Alfonso Nieto-Castanon on 16 Nov 2013

not really sure, but perhaps there are some numerical precision issues for some of the near-colinear cases in the testsuite? (if so perhaps it would be useful to resample the testsuite nodes to remove colinear or near-colinear cases?)

Richard Zapor on 16 Nov 2013

The expected knots table was based upon the Official slow scoring method. The docross function creates many warning messages "Warning: Matrix is singular to working precision. ". A single case, #3, takes >0.3 seconds versus expected 0.01 seconds.

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Problem Tags

gplot knot contest