binary number combination

[gor]

hi
can you please help me with this problem?
i am trying to generate all combinations of binary number with fix number of digits and number of ones
e.g. number of digits=4 and number of ones=2:
0011
0101
0110
1001
1010
1100

have you got any idea how to solve this?
thanks a lot

[v0id]

What language do you want to do this in? This is both a Python and Delphi forum. Kinda odd, now when I'm thinking of it. Maybe Jordan could change it?

Use your favorite search engine for searching on:
"Python permutations"
or, if you're using Delphi:
"Delphi permutations"

[gor]

Originally Posted by v0id

What language do you want to do this in?

delphi

but this is more question about algorithms

[v0id]

Indeed it is, but if you searched on Google using the keywords I said, you would be able to find pages which both covers Delphi and permutations.

If you want information purely about the algorithm itself, then you should check out Wikipedia's article on permutation.

[WingedPanther]

One way to approach it:
Have a for loop from 0 to 2^digits -1.
For each value, do a bitwise and against 1,2,4,8,etc, counting the number of results that are 1. Sum the results (to count the number of 1's) and also concatenate the IntToStrings of the results(to build a string to display). If the sum is 2, then print the string.