bit-manipulation

问题 This question is regarding bitwise copying of class objects. Why is constructor not called, instead destructor is called in below code ? The output is as HowMany h2 = f(h); // No constructor get;s called here.. after construction of h: objectCount = 1 x argument inside f(): objectCount = 1 ~HowMany(): objectCount = 0 after call to f(): objectCount = 0 ~HowMany(): objectCount = -1 ~HowMany(): objectCount = -2 class HowMany { static int objectCount; public: HowMany() { objectCount++; } static

问题 I'm stuck at one problem i.e. to find a subarray whose xor is 0. I read somewhere that this can be done using TRIE data structure but I want the starting and ending indices of the array. For example, consider an array a = [3, 6, 13, 8 15] The subarray from 0 to 3 i.e. [3, 6, 13, 8] has xor equal to 0. (3 xor 6 xor 13 xor 8 = 0) I'm in search for an algorithm than can find those indices ([0, 3] in this case). Detailed answer would be very helpful. Update I tried the brute Force approach find

问题 I understand that: int bit = (number >> 3) & 1; Will give me the bit 3 places from the left, so lets say 8 is 1000 so that would be 0001. What I don't understand is how "& 1" will remove everything but the last bit to display an output of simply "1". I know that this works, I know how to get a bit from an int but how is it the code is extracting the single bit? Code... int number = 8; int bit = (number >> 3) & 1; Console.WriteLine(bit); 回答1: Unless my boolean algebra from school fails me,

问题 In VHDL I want to take a 14 bit input and append '00' on the end to give me a 16 bit number which is the 14 bit input multiplied by 4 and then put this into a 17 bit signed variable such that it is positive (the input is always positive). How should I go about this? like this? shiftedInput <= to_signed('0' & input & '00', 17); Or maybe like this? shiftedInput <= to_signed(input sll 2, 17); Or this? shiftedInput <= to_signed(input & '00', 17); Does it see that the std_logic_vector it's getting

问题 In my last question, nos gave a method of removing the most significant bit from an ASCII character byte, which matches exactly what my professor said when describing the project. My problem is how to strip the significant bit and pack it into a buffer using read and write commands. Since the write command takes in a length in the number of bytes to write, how do I go deeper to the bit level of the buffer array? 回答1: Probably the simplest way to do it is in chunks of eight bytes. Read in a

问题 I'm looking into Vector<T> in the System.Numerics.Vectors namespace from version 4.5.0-preview1-26216-02. MSDN documentation says: Vector<T> is an immutable structure that represents a single vector of a specified numeric type. The count of a Vector<T> instance is fixed , but its upper limit is CPU-register dependent. https://docs.microsoft.com/en-us/dotnet/api/system.numerics.vector-1 (emphasis added) Even overlooking the misguided wording " count [sic.] of a Vector ", this sentence seems

问题 I am making my own simple drawing engine. I am trying to determine if a variable has been set to a specific value using what I think is called bitwise comparison but I maybe wrong. I've always been a bit confused about what the following is and how I use it: int DRAW_REPEAT_X = 70001; // I have a feeling I should make this value binary instead of a unique number, ie, 0 int DRAW_REPEAT_Y = 70002; // I have a feeling I should make this value binary instead of a unique number, ie, 2 int

问题 For my current work on a grid generation algorithm I need an efficient way to transform three-dimensional coordinates to z-order (more precisely: three 4-Byte integers into one 8-Byte integer) and the other way round. This Wikipedia article describes it fairly well: Z-order curve. Since I am not a programmer, the solution I came up with does what it is supposed to do but might be quite naive using the mvbits intrinsic to do the bit interleaving explicitly: SUBROUTINE pos_to_z(i, j, k, zval)

问题 What is the time complexity of * Arithmetic left shift* / * Arithmetic right shift* operators of a n bit operand for example doing x = y << 2; whow much time will it take ? 回答1: Complexity, with the O(…) notation, is an asymptotic characterization of the time an algorithm takes when the input size becomes larger and larger. It is meaningless for algorithms that can take only a finite number of inputs. << can take 2^32 * 32 different inputs, hence a finite number of inputs, therefore it is

问题 I'm writing a Fixedpoint class, but have ran into bit of a snag... The multiplication, division portions, I am not sure how to emulate. I took a very rough stab at the division operator but I am sure it's wrong. Here's what it looks like so far: class Fixed { Fixed(short int _value, short int _part) : value(long(_value + (_part >> 8))), part(long(_part & 0x0000FFFF)) {}; ... inline Fixed operator -() const // example of some of the bitwise it's doing { return Fixed(-value - 1, (~part)