c++ How to sort a vector of bitsets?

Question

I have a vector of bitsets:

vector < bitset<1024> > myvector;

What is the best way to sort this vector from:

0: xxx0100
1: xxx1100
2: xxx0010
3: xxx0001
...
...

to this order:

0: xxx0001
1: xxx0010
2: xxx0100
3: xxx1100
...
...

I already tried to do this with std:sort, but it didn't work, because std:sort use the "<" - operator, which doesn't work for bitsets.

Thanks in advance for your help! Any suggestions or ideas are greatly appreciated!

EDIT:
My question is different to Sorting a vector of custom objects, because it is impossible to use "<"- operator for bitset. So my question is, which operator can I use instead, to compare bitset?

Thank you for your comment! Could you explain me, how to do this? Or give an example? — NPa, Oct 23 '15 at 12:36
Try to do a websearch. Also, make sure you read the documentation concerning the sorting function. — Ulrich Eckhardt, Oct 23 '15 at 17:52

NathanOliver · Accepted Answer · 2015-10-23T18:10:57.683

11

A simple way to sort a std::bitset would be to convert it to a std::string using std::bitset::to_string and then use std::strings operator< to compare the bitsets.

std::vector<std::bitset<128>> data = {1000,2000,80000,15,6000,2};
std::sort(data.begin(), data.end(), [](const auto & lhs, const auto & rhs)
                                    { return lhs.to_string() < rhs.to_string(); });

Live Example

As pointed out in the comments if the bitset is small enough to fit into a unsigned long long then you can use std::bitset::to_ullong and compare the unsigned long longs instead of strings.

edited Oct 23 '15 at 18:10

answered Oct 23 '15 at 18:00

NathanOliver

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@MooingDuck Totally agree but the OP wants to compare bitsets of 1024 bits which cannot be represented as a `unsigned long long` – NathanOliver Oct 23 '15 at 18:09
Totally overlooked that. That makes the `to_ulong` code much more complicated. Alright. – Mooing Duck Oct 23 '15 at 18:14

c++ How to sort a vector of bitsets?

1 Answers1