C++ program to find the type of the given iterator
Given a program that uses an iterator, the task is to find the type of iterator used.
Examples:
Input : vector.begin()
Output : Random_Access IteratorInput : list.begin()
Output : Bidirectional Iterator
There are namely five types of iterators present in the C++ Standard Library which are mentioned below:
Approach:
- Iterator type can be checked by using typeid. typeid is a C++ language operator which returns type identification information at run time. It basically returns a type_info object, which is equality-comparable with other type_info objects.
- Along with it use iterator traits. Traits class defines properties of iterators. Standard algorithms determine certain properties of the iterators passed to them and the range they represent by using the members of the corresponding iterator_traits instantiation.
- Also a iterator category is passed which defines the iterator category the iterator belongs to.
There are five type of tags namely: input_iterator_tag, output_iterator_tag, forward_iterator_tag, bidirectional_iterator_tag, random_access_iterator_tag. - typename is used along with it to provide a type to the iterator during instantiation.
- Now if the iterator category of the input iterator matches the existing iterator categories the result is displayed.
// C++ program to find the type of iterator #include <bits/stdc++.h> using namespace std; template < class T> // function to return the iterator type string get_iterator_type(T it) { // if the iterator category of (it) matches input if ( typeid ( typename iterator_traits<T>::iterator_category) == typeid (input_iterator_tag)) return "Input" ; // if the iterator category of (it) matches output else if ( typeid ( typename iterator_traits<T>::iterator_category) == typeid (output_iterator_tag)) return "Output" ; // if the iterator category of (it) matches forward else if ( typeid ( typename iterator_traits<T>::iterator_category) == typeid (forward_iterator_tag)) return "Forward" ; // if the iterator category of (it) matches bidirectional else if ( typeid ( typename iterator_traits<T>::iterator_category) == typeid (bidirectional_iterator_tag)) return "Bidirectional" ; // if the iterator category of (it) matches random_access else if ( typeid ( typename iterator_traits<T>::iterator_category) == typeid (random_access_iterator_tag)) return "Random_Access" ; // if the iterator category of (it) // does not match any of the above return "Missing" ; } // Driver code int main() { vector< int > v; // iterator that will be checked auto it = v.begin(); cout << get_iterator_type(it) << " Iterator\n" ; return 0; } |
Output:
Random_Access Iterator
Time-Complexity: O(1) to find the iterator type
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