bitset

问题 So I know there is a way to convert Dec to binary using the bitset library but can you do the same for binary to decimal using the bitset library? or do you have to do it manually? bitset<8> bin_x(number); 回答1: You can, but it should be a string. std::bitset<8> bits("1111"); std::cout << bits.to_ulong() << std::endl; You can convert your integer to string and then pass it to bitset c-tor. Live example 来源： https://stackoverflow.com/questions/19627521/c-binary-to-decimal

问题 My source: #include <iostream> #include <bitset> using std::cout; using std::endl; typedef unsigned long long U64; const U64 MAX = 8000000000L; struct Bitmap { void insert(U64 N) {this->s.set(N % MAX);} bool find(U64 N) const {return this->s.test(N % MAX);} private: std::bitset<MAX> s; }; int main() { cout << "Bitmap size: " << sizeof(Bitmap) << endl; Bitmap* s = new Bitmap(); // ... } Compilation command and its output: g++ -g -std=c++11 -O4 tc002.cpp -o latest g++: internal compiler error:

问题 I would like to know what is the memory usage of BitSet in Scala.For example, if I do: var bitArray:BitSet=new BitSet(10) bitArray.add(0) bitArray.add(2) bitArray.add(4) bitArray.add(6) bitArray.add(8) How does that compare with and array containing the even numbers 0,2,4,6,8? What about writing a number in binary: var bitArray:BitSet=new BitSet(32) bitArray.add(5) bitArray.add(3) bitArray.add(2) bitArray.add(1) bitArray.add(0) How does that compare to the number 47? I'm asking here of memory

问题 I searched around and could not find the performance time specifications for bitset::count(). Does anybody know what it is (O(n) or better) and where to find it? EDIT By STL I refer only to the Standard Template Library. 回答1: I read this file (C:\cygwin\lib\gcc\i686-pc-cygwin\3.4.4\include\c++\bitset) on my computer. See these /// Returns the number of bits which are set. size_t count() const { return this->_M_do_count(); } size_t _M_do_count() const { size_t __result = 0; for (size_t __i = 0

问题 The Standard Library class template std::bitset<N> has a constructor (C++11 and onwards, unsigned long argument before C++11) constexpr bitset(unsigned long long) noexcept Contrary to many best-practice guidelines, this single-argument constructor is not marked as explicit . What is the rationale behind this? 回答1: Explicit construction The main objection against an explicit constructor is that copy-initialization from unsigned integers no longer works constexpr auto N = 64; std::bitset<N> b

问题 The Standard Library class template std::bitset<N> has a constructor (C++11 and onwards, unsigned long argument before C++11) constexpr bitset(unsigned long long) noexcept Contrary to many best-practice guidelines, this single-argument constructor is not marked as explicit . What is the rationale behind this? 回答1: Explicit construction The main objection against an explicit constructor is that copy-initialization from unsigned integers no longer works constexpr auto N = 64; std::bitset<N> b

问题 I have a number (power(2,k)) of BitSet objects and I want to store them in a SortedSet . I use the code: Set <BitSet> S= new TreeSet<>(); However, I am getting this error: java.lang.ClassCastException: java.util.BitSet cannot be cast to java.lang.Comparable How do I implement comparable interface? Or is there any other way to sort these elements of type BitSet ? 回答1: There are two ways to use a TreeSet . Have it contain objects that implement Comparable Have a custom Comparator object that

问题 I have bitset<8> v8 and its value is something like "11001101", something in binary, how can we convert it to an array of characters or integers in c++? 回答1: To convert to an array of char, you could use the bitset::to_string() function to obtain the string representation and then copy individual characters from that string: #include <iostream> #include <algorithm> #include <string> #include <bitset> int main() { std::bitset<8> v8 = 0xcd; std::string v8_str = v8.to_string(); std::cout <<

问题 I have multiple threads in my application accessing a BitSet concurrently. The documentation says: A BitSet is not safe for multithreaded use without external synchronization. It doesn't say if it is not safe for reading or writing. Can anybody explain. 回答1: A BitSet is only safe for read-only operations if there is a "happens before" relationship between the last action that initializes the BitSet and the actions that read it. The simplest way to achieve this is using a final . For example:

问题 How do I read a binary file into a bitset or vector<bool> ? The binary file will vary in length. Is there a better container for this? I am new to C++ though experienced as a programmer. 回答1: If the file is large, Why should you read once, whole the file into the memory? You can read a little piece every time. The size is determined with the size in this func: file.read(buff, size) When the buff is char's array. I'm sorry, but You can't simplest read/save vector to file. for more details see