std::vector::max_size
From cppreference.com
                    
                                        
                    
                    
                                                            
                    
|   size_type max_size() const; 
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Returns the maximum number of elements the container is able to hold due to system or library implementation limitations, i.e. std::distance(begin(), end()) for the largest container.
Contents | 
[edit] Parameters
(none)
[edit] Return value
Maximum number of elements.
[edit] Exceptions
| (none) | (until C++11) | 
noexcept specification:   noexcept    | 
(since C++11) | 
[edit] Complexity
Constant.
[edit] Notes
This value is typically equal to std::numeric_limits<size_type>::max(), and reflects the theoretical limit on the size of the container. At runtime, the size of the container may be limited to a value smaller than max_size() by the amount of RAM available.
See also
|    returns the number of elements   (public member function)  | 
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|    returns the number of elements that can be held in currently allocated storage   (public member function)  |