How can i do a Bitwise OR on strings?
A:
10001
01010
------
11011
Why on strings? The Bits can have length of 40-50.Maybe this could be problematic on int ? Any Ideas ?
+3
A:
You should take a look at the C++ std::bitset class, which does exactly what you want.
anon
2010-03-30 11:47:36
http://www.sgi.com/tech/stl/bitset.html
RickNotFred
2010-03-30 11:50:00
+1
A:
Why not just use a vector of int values? Doesn't the bitset still use a byte per bit?
You can also use a vector of bool values, but this is also implementation specific.
Depending on whether you need storage efficiency or speed (or the utility of container methods that a couple of these approaches lack) you might profile to decide which approach to use.
Alex Reynolds
2010-03-30 11:48:09
After a brief Google search, others seem to claim that bitset is not part of the STL standard, and that it does not follow STL container conventions. I'm sure it is a workable option, though.
Alex Reynolds
2010-03-30 12:00:21
Others can claim away - it is part of the C++ Standard - see section 23.3.5 describing it.
anon
2010-03-30 12:02:39
@Neil @Alex bitset is part of the C++ Standard but as far as I can tell there's no specification of how it's stored, using a byte (or even an int) per bit seems legit.
Andreas Brinck
2010-03-30 12:03:02
@andreas The storage is not specified, but no-one would use the thing if it did not in fact store individual bits. That's one reason why they are fixed-sized.
anon
2010-03-30 12:05:21
I have used vectors of `int` and `bool` values in the past, but the use of `bool` vectors is also implementation specific. So probably the best thing to do is profile different approaches, and use whichever is faster or more memory efficient for that platform.
Alex Reynolds
2010-03-30 12:07:29
@Alex I think you are using a specialmeaning of the term "implementation specific". vector <bool> is also standardised (unfortunately, perhaps).
anon
2010-03-30 12:10:56
+1
A:
For each char:
char result = (a - '0') | (b - '0') + '0';
Where a and b are two chars with ascii character 0 or 1 in them.
Andreas Brinck
2010-03-30 11:50:17
+7
A:
I would say std::bitset is more than enough for your situation, but for more flexibility you can use boost::dynamic_bitset. Here is an example on std::bitset:
const size_t N = 64;
string a_str = "10001", b_str = "01010";
bitset<N> a(a_str), b(b_str);
bitset<N> c = a | b;
cout << c;
AraK
2010-03-30 11:51:13
A:
This is similar to Andreas Brinck's answer, only it returns a full output string and can compare strings of different (arbitrary) lengths.
Example in C# (not near c++ compiler right now), but it should be simple to convert it to a language of your choice.
public static string BitwiseOr(string input1, string input2)
{
char[] inarr1 = (char[])input1.ToCharArray().Reverse().ToArray();
char[] inarr2 = (char[])input2.ToCharArray().Reverse().ToArray();
char[] outarr = new char[input1.Length > input2.Length ? input1.Length : input2.Length];
for (int i = 0; i < outarr.Length ; i++)
{
char c1 = i < input1.Length ? inarr1[i] : '0';
char c2 = i < input2.Length ? inarr2[i] : '0';
outarr[i] = (char)((c1 - '0') | (c2 - '0') + '0');
}
return new string((char[])outarr.Reverse().ToArray());
}
Of course this is only valid if you really need it to be in a string, if not you should (as suggested in other answers) use a vector or similar data type.
Rekreativc
2010-03-30 12:15:17