问题
I'm implementing a binary representation of an equal-side bi-partitioning algorithm and I'm wondering what the best way to iterate through all combinations of N bits that have equal (N/2) 1's and 0's. I'm trying to find the quickest way, not the easiest to code. Thanks.
回答1:
It's just (N choose N/2); you're choosing which bits are 0s, the rest are 1s.
If you have 10 bits, and you want 5 zeroes and 5 ones, there are (10 choose 5) = 252 possibilities.
See also:
- Algorithm to return all combinations of k elements from n
As has been pointed out, this number is the binomial coefficient (n k). When k is n/2 is when this coefficient is the largest; I'm sure you're aware that there are numerous possibilities, which is why you wanted the fastest algorithm to generate them.
Instead of micro-optimizing this generator to make it the fastest possible, I'd first exhaust all other options: are you sure you can't do any better than trying all possibilities? This brute force solution does not scale.
Try to find a better algorithm if at all possible.
来源：https://stackoverflow.com/questions/2635019/counting-through-all-binary-numbers-with-equal-1s-and-0s