Robert Voigtländer wrote: > Hi, > > I need to generate all variants of a 2D array with variable dimension > sizes which fit a specific rule. (up to 200*1000) > > The rules are: > - Values are only 0 or 1 > - the sum of each line bust be 1 > - only valid results must be generated (generating all and only returning > the valid results takes to long; that's what I tried already) > > So for a 2x2 array these would be the valid results: > > 10 > 01 > > 01 > 10 > > 10 > 10 > > 01 > 01 > > > Must be possible with nested loops and a counter per line. But I don't get > it. > > Can someone help?
Have a look at itertools.product(). If you need to code it in Python -- the documentation has an example implementation. from itertools import product def f(n): rows = [[0] * n for i in range(n)] for i, row in enumerate(rows): row[i] = 1 rows = [tuple(row) for row in rows] return list(product(rows, repeat=n)) if __name__ == "__main__": from pprint import pprint pprint(f(2)) print("---") pprint(f(3)) However, n**n is growing quite fast; you'll soon reach the limits of what is feasible in Python. Maybe numpy has something to offer to push these limits a bit. An optimisation would be to store the position of the 1, i. e. 01 10 00 11 for n=2. If you reorder these you get 0, 1, 2, 3. I think I'm seeing a pattern... -- https://mail.python.org/mailman/listinfo/python-list