En Sat, 15 Mar 2008 18:57:36 -0200, Ravi Kumar <[EMAIL PROTECTED]> escribi�:
> An Interesting problem, > """ > A man has only 4 bricks of different weights, lies between 1-40KG, > Also, the total weights of Brick A, B, C, D (ie A+B+C+D) is 40KG. > The man uses that brick to calculate every possible weight > from 1 KG to 40 KG in his shop. (only whole numbers 1KG, 2KG etc, not > like > 2.3KG) > """ > > I thought it would really be good to solve it by python, and right now on > the mid-way solving using very dirty approach. > But I feel, using SETs with python in such would solve it better. > Can anyone come with good solution, and maybe solution showing usage of > Sets. This isn't specifically Python problem; some hints anyway: a) Any integer can be written as a base-3 number (anyone knows base-10 numbers, and you know base-2/binary numbers, I presume). x = a[n]*3**n + a[n-1]*3**(n-1) + ... + a[1]*3 + a[0] where all a[i] are either 0, 1 or 2 b) 2*3**n = (3-1)*3**n = 3**(n+1) - 3**n So you can replace every a[i]==2 in the a) expression with (-1), adding +1 to the coefficient to the left (why?). You end up with an expression involving only +1 and -1 coefficients (why?) c) You can compare, add and substract weights using an old two-plate balance. -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
