> --------------------- I have a question. in the LIST M= [[1,1,1,1], [0,1,1,1], [1,1,0,1], [1,1,1,1]] If treat them as the locations of 16 points, I want to generate another list N to hold the corresponding value for each point to its nearest 0. > ------------------
Your explanation of the problem is clear up to this point, but... > ----------------------- For example: the nearest 0 point to M[0][0] is M[1][0], so N[0][0]=1; > ---------------------- You lost me there, how do you calculate the 1? Is it the linear distance? The number of hops? related to the index numbering? I'm confused. > M[0][1]'s nearest 0 is also at M[1][0], so N[0][1]=2; Linearly this is root 2 in distance not 2 so I assume you are counting hops? > but N[0][3]=3 because 0 at M[2][2] is much nearer; If you are counting hops then 3 is valid but its only one hop nearer not *much* nearer! > ------------------- N should be [[1,2,2,3], [0,1,1,2], [1,1,0,1], [2,2,1,2]] > ------------------- Assuming you mean hops... (and there probably is a proper mathematical algorithm for this.) I would do this: Locate the first zero(1,1) in this case. Mark all boxes with their distance to it. N looks like this (forget the python syntax for now, focus on the problem): 1234 0123 1234 2345 Can you figure out the algorithm for doing that? Now find the next zero in M and do the same, except you only overwrite values where the new value is less than previously. Thus the values: 4323 3212 2101 3212 becomes 1223 0112 1101 2212 when overlaid on the previous matrix. Which is your required matrix N - QED. Does that help? Alan G Author of the learn to program web tutor http://www.freenetpages.co.uk/hp/alan.gauld _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
