I know in C++11 they added the feature to initialize a variable to zero as such
double number = {}; // number = 0 int data{}; // data = 0 Is there a similar way to initialize a std::vector of a fixed length to all zero's?
4 Answers
You don't need initialization lists for that:
std::vector<int> vector1(length, 0); std::vector<double> vector2(length, 0.0); 6 Comments
daniel gratzer
You don't need to explicitly state the 0 do you? just
vector(length) should work?
ronag
@jozefg: Yes, it would work, though there is no harm in being explicit about what you want the code to do.
Johannes Schaub - litb
@ronag i wrote my own answer because being explicit in this case is not necessarily a good example if int is not the type he is working with. gereral programming is available in c++ but when i was reminded that you can omit the argument altogether, i removed my answer.
Ankit Mishra
Is it possible to re-initialized Global Vector's all element with
ZERO with efficiently without using for loops??????
Y.T.
@AnkitMishra Yes, use
std:fill(vector2.begin(), vector2.end(), 0) |
With recent versions of c++ you can go with std::fill.
I noticed someone mentioned it as comment. But should be an answer and encourage to use standard library algorithms which are mentioned by experts, very well tested and proven.
std::vector<int> vecOfInts; vecOfInts.resize(10); std::fill(vecOfInts.begin(), vecOfInts.end(), 0); for (auto const& intVal : vecOfInts) { std::cout << intVal << " "; } 4 Comments
Maf
What's putting 10 values in your vector is the resize method, not the fill which just replaces existing values.
Pavan Chandaka
The OP specifies "fixed length" in his question. 10 is an example.
diverger
This is a method to assign a vector to 0's, but the OP specified 'initialize'.
Luiz Doleron
You needn't fill. vecOfInts.resize(10, 0) does the job
Initializing a vector having struct, class or Union can be done this way
std::vector<SomeStruct> someStructVect(length); memset(someStructVect.data(), 0, sizeof(SomeStruct)*length); 
2 Comments
Alexander Malakhov
This is OK for built-in types (
int etc) and PODs, but will bring huge problems for classes with either 1. virtual methods (because vtable pointer will be set to 0) or 2. invariant that some field is not 0 (which is usually enforced by constructors and methods).
underscore_d
As well as being dangerous for anything except trivial types, what you wrote is pointless: constructing the vector with size
length already default-initialises all of the new elements. If it were needed to default-initialise all elements later, or to set them all to some other value, std::fill() should be used because it's actually C++ and type-safe.For c++: Let's say that the vector has a maximum of 100 int elements. You can initialize it this way:
int vector[100]={0};
2 Comments
ABaumstumpf
That is NOT a vector.
ReinstateMonica3167040
More importantly, you actually get zero initialization for free with arrays. Try
int array[100]; — it's zero-filled.
std::vector<int> vec(42);