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Difference between revisions of "cpp/container/unordered multiset/contains"

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Revision as of 23:30, 10 June 2018

[edit template]
 
C++
 
Containers library
 
std::unordered_multiset
Member types
Member functions
Non-member functions
(until C++20)
Deduction guides (C++17)
 
bool contains( const Key& key ) const;
 (1) (since C++20)
template< class K >
bool contains( const K& x ) const;
 (2) (since C++20)
1) Checks if there is an element with key equivalent to key in the container.
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.

Contents

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 multiset>
 
int main()
{
    std::unordered multiset<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

 finds element with specific key
(public member function) [edit]
returns the number of elements matching specific key
(public member function) [edit]
returns range of elements matching a specific key
(public member function) [edit]
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