Memset on vector C++

Question

Is there any equivalent function of memset for vectors in C++ ?

(Not clear() or erase() method, I want to retain the size of vector, I just want to initialize all the values.)

Answer 1

Use std::fill():

std::fill(myVector.begin(), myVector.end(), 0); 

Answer 2

If your vector contains POD types, it is safe to use memset on it - the storage of a vector is guaranteed to be contiguous.

memset(&vec[0], 0, sizeof(vec[0]) * vec.size()); 

Edit: Sorry to throw an undefined term at you - POD stands for Plain Old Data, i.e. the types that were available in C and the structures built from them.

Edit again: As pointed out in the comments, even though bool is a simple data type, vector<bool> is an interesting exception and will fail miserably if you try to use memset on it. Adam Rosenfield's answer still works perfectly in that case.