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std::unorde...t::contains(3)   C++ Standard Libary  std::unorde...t::contains(3)

NAME
     std::unordered_set::contains - std::unordered_set::contains

Synopsis
	bool contains( const Key& key ) const; (1) (since C++20)
	template< class K >		       (2) (since C++20)
	bool contains( const K& x ) const;

	1)  Checks if there is an element with key equivalent to key in the con-
     tainer.
	2) Checks if there is an element with key that	compares  equivalent  to
     the value x.
	This	overload   participates   in   overload   resolution   only   if
     Hash::is_transparent and
	KeyEqual::is_transparent are valid and each denotes a type. This assumes
     that such
	Hash is callable with both K and Key type,  and  that  the  KeyEqual  is
     transparent,
	which,	together,  allows  calling this function without constructing an
     instance of
	Key.

Parameters
	key - key value of the element to search for
	x   - a value of any type that can be transparently compared with a key

Return value
	true if there is such an element, otherwise false.

Complexity
	Constant on average, worst case linear in the size of the container.

Example
     // Run this code

      #include <iostream>
      #include <unordered_set>

      int main()
      {
	  std::unordered_set<int> example{1, 2, 3, 4};

	  for (int x : {2, 5})
	      if (example.contains(x))
		  std::cout << x << ": Found\n";
	      else
		  std::cout << x << ": Not found\n";
      }

Output:
      2: Found
      5: Not found

See also
	find	    finds element with specific key
		    (public member function)
	count	    returns the number of elements matching specific key
		    (public member function)
	equal_range returns range of elements matching a specific key
		    (public member function)

http://cppreference.com 	   2024.06.10	    std::unorde...t::contains(3)
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