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      std::multimap<Key,T,Compare,Allocator>::equal_range

      From cppreference.com
      <cpp‎ |container‎ |multimap

      [edit template]
       
       
       
      std::multimap
      Member functions
      Non-member functions
      (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
      Deduction guides(C++17)
       
      std::pair<iterator, iterator> equal_range(const Key& key);
      		 (1)(constexpr since C++26)
      std::pair<const_iterator, const_iterator>
          equal_range(const Key& key)const;
      		 (2)(constexpr since C++26)
      template<class K>
      std::pair<iterator, iterator> equal_range(const K& x);
      		 (3)(since C++14)
      (constexpr since C++26)
      template<class K>

      std::pair<const_iterator, const_iterator>

          equal_range(const K& x)const;
      		 (4)(since C++14)
      (constexpr since C++26)

      Returns a range containing all elements with the given key in the container. The range is defined by two iterators, one pointing to the first element that isnot less than the given key and another pointing to the first element greater than the given key.

      Alternatively, the first iterator may be obtained withlower_bound(), and the second withupper_bound().

      1,2) Compares the keys tokey.
      3,4) Compares the keys to the valuex.
      This overload participates in overload resolution only ifCompare istransparent. It allows calling this function without constructing an instance ofKey.

      Contents

      [edit]Parameters

      key - key value to compare the elements to
      x - alternative value that can be compared toKey

      [edit]Return value

      std::pair containing a pair of iterators defining the wanted range:

      • The first iterator points to the first element not less than the given key, orend() if no such element exists.
      • The second iterator points to the first element greater than the given key, orend() if no such element exists.

      Sinceemplace and unhintedinsert always insert at the upper bound, the order of equivalent elements in the equal range is the order of insertion unless hintedinsert oremplace_hint was used to insert an element at a different position.

      		(since C++11)

      [edit]Complexity

      Logarithmic in the size of the container.

      Notes

      Feature-test macroValueStdFeature
      __cpp_lib_generic_associative_lookup201304L(C++14)Heterogeneous comparison lookup inassociative containers, for overloads(3,4)

      [edit]Example

      Run this code
      #include <iostream>#include <map> int main(){std::multimap<int,char> dict{{1,'A'},{2,'B'},{2,'C'},{2,'D'},{4,'E'},{3,'F'}}; auto range= dict.equal_range(2); for(auto i= range.first; i!= range.second;++i)std::cout<< i->first<<": "<< i->second<<'\n';}

      Output:

      2: B2: C2: D

      [edit]See also

      finds element with specific key
      (public member function)[edit]
      (C++20)
      		 checks if the container contains element with specific key
      (public member function)[edit]
      returns the number of elements matching specific key
      (public member function)[edit]
      returns an iterator to the first elementgreater than the given key
      (public member function)[edit]
      returns an iterator to the first elementnot less than the given key
      (public member function)[edit]
      returns range of elements matching a specific key
      (function template)[edit]
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