What is the difference between cbegin and begin fo

问题:

The member begin has two overloadings one of them is const_iterator begin() const;. There's also the cbegin const_iterator cbegin() const noexcept;. Both of them returns const_iterator to the begin of a list. What's the difference?

回答1:

begin will return an iterator or a const_iterator depending on the const-qualification of the object it is called on.

cbegin will return a const_iterator unconditionally.

std::vector<int> vec;
const std::vector<int> const_vec;

vec.begin(); //iterator
vec.cbegin(); //const_iterator

const_vec.begin(); //const_iterator
const_vec.cbegin(); //const_iterator