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‎docs/standard-library/map-class.md‎

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---
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title: "map Class"
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ms.date: "10/18/2018"
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f1_keywords: ["map/std::map", "map/std::map::allocator_type", "map/std::map::const_iterator", "map/std::map::const_pointer", "map/std::map::const_reference", "map/std::map::const_reverse_iterator", "map/std::map::difference_type", "map/std::map::iterator", "map/std::map::key_compare", "map/std::map::key_type", "map/std::map::mapped_type", "map/std::map::pointer", "map/std::map::reference", "map/std::map::reverse_iterator", "map/std::map::size_type", "map/std::map::value_type", "map/std::map::at", "map/std::map::begin", "map/std::map::cbegin", "map/std::map::cend", "map/std::map::clear", "map/std::map::count", "map/std::map::crbegin", "map/std::map::crend", "map/std::map::emplace", "map/std::map::emplace_hint", "map/std::map::empty", "map/std::map::end", "map/std::map::equal_range", "map/std::map::erase", "map/std::map::find", "map/std::map::get_allocator", "map/std::map::insert", "map/std::map::key_comp", "map/std::map::lower_bound", "map/std::map::max_size", "map/std::map::rbegin", "map/std::map::rend", "map/std::map::size", "map/std::map::swap", "map/std::map::upper_bound", "map/std::map::value_comp"]
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helpviewer_keywords: ["std::map [C++]", "std::map [C++], allocator_type", "std::map [C++], const_iterator", "std::map [C++], const_pointer", "std::map [C++], const_reference", "std::map [C++], const_reverse_iterator", "std::map [C++], difference_type", "std::map [C++], iterator", "std::map [C++], key_compare", "std::map [C++], key_type", "std::map [C++], mapped_type", "std::map [C++], pointer", "std::map [C++], reference", "std::map [C++], reverse_iterator", "std::map [C++], size_type", "std::map [C++], value_type", "std::map [C++], at", "std::map [C++], begin", "std::map [C++], cbegin", "std::map [C++], cend", "std::map [C++], clear", "std::map [C++], count", "std::map [C++], crbegin", "std::map [C++], crend", "std::map [C++], emplace", "std::map [C++], emplace_hint", "std::map [C++], empty", "std::map [C++], end", "std::map [C++], equal_range", "std::map [C++], erase", "std::map [C++], find", "std::map [C++], get_allocator", "std::map [C++], insert", "std::map [C++], key_comp", "std::map [C++], lower_bound", "std::map [C++], max_size", "std::map [C++], rbegin", "std::map [C++], rend", "std::map [C++], size", "std::map [C++], swap", "std::map [C++], upper_bound", "std::map [C++], value_comp"]
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ms.date: "9/9/2020"
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f1_keywords: ["map/std::map", "map/std::map::allocator_type", "map/std::map::const_iterator", "map/std::map::const_pointer", "map/std::map::const_reference", "map/std::map::const_reverse_iterator", "map/std::map::difference_type", "map/std::map::iterator", "map/std::map::key_compare", "map/std::map::key_type", "map/std::map::mapped_type", "map/std::map::pointer", "map/std::map::reference", "map/std::map::reverse_iterator", "map/std::map::size_type", "map/std::map::value_type", "map/std::map::at", "map/std::map::begin", "map/std::map::cbegin", "map/std::map::cend", "map/std::map::clear", "map/std::map::count", "map/std::map::contains", "map/std::map::crbegin", "map/std::map::crend", "map/std::map::emplace", "map/std::map::emplace_hint", "map/std::map::empty", "map/std::map::end", "map/std::map::equal_range", "map/std::map::erase", "map/std::map::find", "map/std::map::get_allocator", "map/std::map::insert", "map/std::map::key_comp", "map/std::map::lower_bound", "map/std::map::max_size", "map/std::map::rbegin", "map/std::map::rend", "map/std::map::size", "map/std::map::swap", "map/std::map::upper_bound", "map/std::map::value_comp"]
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helpviewer_keywords: ["std::map [C++]", "std::map [C++], allocator_type", "std::map [C++], const_iterator", "std::map [C++], const_pointer", "std::map [C++], const_reference", "std::map [C++], const_reverse_iterator", "std::map [C++], difference_type", "std::map [C++], iterator", "std::map [C++], key_compare", "std::map [C++], key_type", "std::map [C++], mapped_type", "std::map [C++], pointer", "std::map [C++], reference", "std::map [C++], reverse_iterator", "std::map [C++], size_type", "std::map [C++], value_type", "std::map [C++], at", "std::map [C++], begin", "std::map [C++], cbegin", "std::map [C++], cend", "std::map [C++], clear", "std::map [C++], count", "std::map [C++], contains", "std::map [C++], crbegin", "std::map [C++], crend", "std::map [C++], emplace", "std::map [C++], emplace_hint", "std::map [C++], empty", "std::map [C++], end", "std::map [C++], equal_range", "std::map [C++], erase", "std::map [C++], find", "std::map [C++], get_allocator", "std::map [C++], insert", "std::map [C++], key_comp", "std::map [C++], lower_bound", "std::map [C++], max_size", "std::map [C++], rbegin", "std::map [C++], rend", "std::map [C++], size", "std::map [C++], swap", "std::map [C++], upper_bound", "std::map [C++], value_comp"]
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ms.assetid: 7876f4c9-ebb4-4878-af1e-09364c43af0a
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---
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# map Class
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|Member function|Description|
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|-|-|
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|[at](#at)|Finds an element with a specified key value.|
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|[begin](#begin)|Returns an iterator that points to the first element in the map.|
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|[cbegin](#cbegin)|Returns a const iterator that points to the first element in the map.|
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|[at](#at)|Finds an element with the specified key value.|
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|[begin](#begin)|Returns an iterator that points to the first element in the `map`.|
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|[cbegin](#cbegin)|Returns a const iterator that points to the first element in the `map`.|
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|[cend](#cend)|Returns a const past-the-end iterator.|
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|[clear](#clear)|Erases all the elements of a map.|
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|[clear](#clear)|Erases all the elements of a `map`.|
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|[contains](#contains)|Checks if there is an element with the specified key in the `map`.|
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|[count](#count)|Returns the number of elements in a map whose key matches the key specified in a parameter.|
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|[crbegin](#crbegin)|Returns a const iterator that points to the first element in a reversed map.|
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|[crend](#crend)|Returns a const iterator that points to the location after the last element in a reversed map.|
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|[emplace](#emplace)|Inserts an element constructed in place into the map.|
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|[emplace_hint](#emplace_hint)|Inserts an element constructed in place into the map, with a placement hint.|
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|[empty](#empty)|Returns **`true`** if a map is empty.|
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|[crbegin](#crbegin)|Returns a const iterator that points to the first element in a reversed `map`.|
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|[crend](#crend)|Returns a const iterator that points to the location after the last element in a reversed `map`.|
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|[emplace](#emplace)|Inserts an element constructed in place into the `map`.|
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|[emplace_hint](#emplace_hint)|Inserts an element constructed in place into the `map`, with a placement hint.|
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|[empty](#empty)|Returns **`true`** if a `map` is empty.|
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|[end](#end)|Returns the past-the-end iterator.|
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|[equal_range](#equal_range)|Returns a pair of iterators. The first iterator in the pair points to the first element in a `map` with a key that is greater than a specified key. The second iterator in the pair points to the first element in the `map` with a key that is equal to or greater than the key.|
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|[erase](#erase)|Removes an element or a range of elements in a map from the specified positions.|
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|[find](#find)|Returns an iterator that points to the location of an element in a map that has a key equal to a specified key.|
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|[get_allocator](#get_allocator)|Returns a copy of the `allocator` object that is used to construct the map.|
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|[insert](#insert)|Inserts an element or a range of elements into the map at a specified position.|
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|[key_comp](#key_comp)|Returns a copy of the comparison object that used to order keys in a map.|
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|[lower_bound](#lower_bound)|Returns an iterator to the first element in a map that has a key value that is equal to or greater than that of a specified key.|
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|[max_size](#max_size)|Returns the maximum length of the map.|
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|[rbegin](#rbegin)|Returns an iterator that points to the first element in a reversed map.|
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|[rend](#rend)|Returns an iterator that points to the location after the last element in a reversed map.|
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|[find](#find)|Returns an iterator that points to the location of an element in a `map` that has a key equal to a specified key.|
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|[get_allocator](#get_allocator)|Returns a copy of the `allocator` object that is used to construct the `map`.|
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|[insert](#insert)|Inserts an element or a range of elements into the `map` at a specified position.|
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|[key_comp](#key_comp)|Returns a copy of the comparison object that used to order keys in a `map`.|
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|[lower_bound](#lower_bound)|Returns an iterator to the first element in a `map` that has a key value that is equal to or greater than that of a specified key.|
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|[max_size](#max_size)|Returns the maximum length of the `map`.|
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|[rbegin](#rbegin)|Returns an iterator that points to the first element in a reversed m`ap.|
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|[rend](#rend)|Returns an iterator that points to the location after the last element in a reversed `map`.|
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|[size](#size)|Returns the number of elements in the map.|
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|[swap](#swap)|Exchanges the elements of two maps.|
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|[upper_bound](#upper_bound)|Returns an iterator to the first element in a map that has a key value that is greater than that of a specified key.|
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|[value_comp](#value_comp)|Retrieves a copy of the comparison object that is used to order element values in a map.|
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|[upper_bound](#upper_bound)|Returns an iterator to the first element in a `map` that has a key value that is greater than that of a specified key.|
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|[value_comp](#value_comp)|Retrieves a copy of the comparison object that is used to order element values in a `map`.|
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### Operators
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The number of elements in m1 with a sort key of 3 is: 0.
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```
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## <a name="contains"></a> contains
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Checks if there is an element the specified key in the `map` .
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```cpp
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[[nodiscard]] bool contains(const K& key) const;
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```
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### Parameters
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*key*\
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The element's key value to look for.
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### Return Value
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`true` if the element is found in the container; `false` otherwise.
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### Remarks
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`Contains()` is new in C++20. To use it, specify the [std:c++latest](../build/reference/std-specify-language-standard-version.md) compiler option.
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### Example
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```cpp
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// Requires /std:c++latest
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#include <map>
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#include <iostream>
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int main()
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{
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std::map<int, bool> theMap = {{0, true},{1, false}};
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std::cout << std::boolalpha << theMap.contains(1) << '\n';
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std::cout << std::boolalpha << theMap.contains(2) << '\n';
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}
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```
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```Output
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true
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false
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```
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## <a name="crbegin"></a> crbegin
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Returns a const iterator addressing the first element in a reversed map.

‎docs/standard-library/multimap-class.md‎

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title: "multimap Class"
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ms.date: "10/18/2018"
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f1_keywords: ["map/std::multimap", "map/std::multimap::allocator_type", "map/std::multimap::const_iterator", "map/std::multimap::const_pointer", "map/std::multimap::const_reference", "map/std::multimap::const_reverse_iterator", "map/std::multimap::difference_type", "map/std::multimap::iterator", "map/std::multimap::key_compare", "map/std::multimap::key_type", "map/std::multimap::mapped_type", "map/std::multimap::pointer", "map/std::multimap::reference", "map/std::multimap::reverse_iterator", "map/std::multimap::size_type", "map/std::multimap::value_type", "map/std::multimap::begin", "map/std::multimap::cbegin", "map/std::multimap::cend", "map/std::multimap::clear", "map/std::multimap::count", "map/std::multimap::crbegin", "map/std::multimap::crend", "map/std::multimap::emplace", "map/std::multimap::emplace_hint", "map/std::multimap::empty", "map/std::multimap::end", "map/std::multimap::equal_range", "map/std::multimap::erase", "map/std::multimap::find", "map/std::multimap::get_allocator", "map/std::multimap::insert", "map/std::multimap::key_comp", "map/std::multimap::lower_bound", "map/std::multimap::max_size", "map/std::multimap::rbegin", "map/std::multimap::rend", "map/std::multimap::size", "map/std::multimap::swap", "map/std::multimap::upper_bound", "map/std::multimap::value_comp"]
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helpviewer_keywords: ["std::multimap [C++]", "std::multimap [C++], allocator_type", "std::multimap [C++], const_iterator", "std::multimap [C++], const_pointer", "std::multimap [C++], const_reference", "std::multimap [C++], const_reverse_iterator", "std::multimap [C++], difference_type", "std::multimap [C++], iterator", "std::multimap [C++], key_compare", "std::multimap [C++], key_type", "std::multimap [C++], mapped_type", "std::multimap [C++], pointer", "std::multimap [C++], reference", "std::multimap [C++], reverse_iterator", "std::multimap [C++], size_type", "std::multimap [C++], value_type", "std::multimap [C++], begin", "std::multimap [C++], cbegin", "std::multimap [C++], cend", "std::multimap [C++], clear", "std::multimap [C++], count", "std::multimap [C++], crbegin", "std::multimap [C++], crend", "std::multimap [C++], emplace", "std::multimap [C++], emplace_hint", "std::multimap [C++], empty", "std::multimap [C++], end", "std::multimap [C++], equal_range", "std::multimap [C++], erase", "std::multimap [C++], find", "std::multimap [C++], get_allocator", "std::multimap [C++], insert", "std::multimap [C++], key_comp", "std::multimap [C++], lower_bound", "std::multimap [C++], max_size", "std::multimap [C++], rbegin", "std::multimap [C++], rend", "std::multimap [C++], size", "std::multimap [C++], swap", "std::multimap [C++], upper_bound", "std::multimap [C++], value_comp"]
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ms.date: "9/9/2020"
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f1_keywords: ["map/std::multimap", "map/std::multimap::allocator_type", "map/std::multimap::const_iterator", "map/std::multimap::const_pointer", "map/std::multimap::const_reference", "map/std::multimap::const_reverse_iterator", "map/std::multimap::difference_type", "map/std::multimap::iterator", "map/std::multimap::key_compare", "map/std::multimap::key_type", "map/std::multimap::mapped_type", "map/std::multimap::pointer", "map/std::multimap::reference", "map/std::multimap::reverse_iterator", "map/std::multimap::size_type", "map/std::multimap::value_type", "map/std::multimap::begin", "map/std::multimap::cbegin", "map/std::multimap::cend", "map/std::multimap::clear", "map/std::multimap::contains", "map/std::multimap::count", "map/std::multimap::crbegin", "map/std::multimap::crend", "map/std::multimap::emplace", "map/std::multimap::emplace_hint", "map/std::multimap::empty", "map/std::multimap::end", "map/std::multimap::equal_range", "map/std::multimap::erase", "map/std::multimap::find", "map/std::multimap::get_allocator", "map/std::multimap::insert", "map/std::multimap::key_comp", "map/std::multimap::lower_bound", "map/std::multimap::max_size", "map/std::multimap::rbegin", "map/std::multimap::rend", "map/std::multimap::size", "map/std::multimap::swap", "map/std::multimap::upper_bound", "map/std::multimap::value_comp"]
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helpviewer_keywords: ["std::multimap [C++]", "std::multimap [C++], allocator_type", "std::multimap [C++], const_iterator", "std::multimap [C++], const_pointer", "std::multimap [C++], const_reference", "std::multimap [C++], const_reverse_iterator", "std::multimap [C++], difference_type", "std::multimap [C++], iterator", "std::multimap [C++], key_compare", "std::multimap [C++], key_type", "std::multimap [C++], mapped_type", "std::multimap [C++], pointer", "std::multimap [C++], reference", "std::multimap [C++], reverse_iterator", "std::multimap [C++], size_type", "std::multimap [C++], value_type", "std::multimap [C++], begin", "std::multimap [C++], cbegin", "std::multimap [C++], cend", "std::multimap [C++], clear", "std::multimap [C++], contains", "std::multimap [C++], count", "std::multimap [C++], crbegin", "std::multimap [C++], crend", "std::multimap [C++], emplace", "std::multimap [C++], emplace_hint", "std::multimap [C++], empty", "std::multimap [C++], end", "std::multimap [C++], equal_range", "std::multimap [C++], erase", "std::multimap [C++], find", "std::multimap [C++], get_allocator", "std::multimap [C++], insert", "std::multimap [C++], key_comp", "std::multimap [C++], lower_bound", "std::multimap [C++], max_size", "std::multimap [C++], rbegin", "std::multimap [C++], rend", "std::multimap [C++], size", "std::multimap [C++], swap", "std::multimap [C++], upper_bound", "std::multimap [C++], value_comp"]
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ms.assetid: 8796ae05-37c4-475a-9e61-75fde9d4a463
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# multimap Class
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|[cbegin](#cbegin)|Returns a const iterator addressing the first element in the `multimap`.|
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|[cend](#cend)|Returns a const iterator that addresses the location succeeding the last element in a `multimap`.|
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|[clear](#clear)|Erases all the elements of a `multimap`.|
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|[contains](#contains)|Checks if there is an element with the specified key in the `multimap`.|
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|[count](#count)|Returns the number of elements in a `multimap` whose key matches a parameter-specified key.|
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|[crbegin](#crbegin)|Returns a const iterator addressing the first element in a reversed `multimap`.|
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|[crend](#crend)|Returns a const iterator that addresses the location succeeding the last element in a reversed `multimap`.|
@@ -406,6 +407,48 @@ To access the value of the key for the element, use `crIter->first`, which is eq
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See the example for [rend](#rend) for an example of how to declare and use `const_reverse_iterator`.
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## <a name="contains"></a> contains
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Checks if there is an element the specified key in the `multimap` .
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```cpp
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[[nodiscard]] bool contains(const K& key) const;
416+
```
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### Parameters
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*key*\
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The element's key value to look for.
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### Return Value
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`true` if the element is found in the container; `false` otherwise.
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### Remarks
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`Contains()` is new in C++20. To use it, specify the [std:c++latest](../build/reference/std-specify-language-standard-version.md) compiler option.
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### Example
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```cpp
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// Requires /std:c++latest
435+
#include <map>
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#include <iostream>
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int main()
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{
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std::multimap<int, bool> theMultiMap = {{0, false}, {1, true}};
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std::cout << std::boolalpha << theMultiMap.contains(1) << '\n';
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std::cout << std::boolalpha << theMultiMap.contains(2) << '\n';
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}
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```
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```Output
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true
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false
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```
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## <a name="count"></a> multimap::count
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Returns the number of elements in a multimap whose keys match a parameter-specified key.

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