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      std::flat_set<Key,Compare,KeyContainer>::insert

      From cppreference.com
      <cpp‎ |container‎ |flat set
       
       
       
       
      std::pair<iterator,bool> insert(const value_type& value);
      		 (1)(since C++23)
      std::pair<iterator,bool> insert( value_type&& value);
      		 (2)(since C++23)
      iterator insert( const_iterator pos,const value_type& value);
      		 (3)(since C++23)
      iterator insert( const_iterator pos, value_type&& value);
      		 (4)(since C++23)
      template<class K>
      iterator insert( const_iterator pos, K&& x);
      		 (5)(since C++23)
      template<class InputIt>
      void insert( InputIt first, InputIt last);
      		 (6)(since C++23)
      template<class K>
      std::pair<iterator,bool> insert( K&& x);
      		 (7)(since C++23)
      template<class InputIt>
      void insert(std::sorted_unique_t, InputIt first, InputIt last);
      		 (8)(since C++23)
      void insert(std::initializer_list<key_type> ilist);
      		 (9)(since C++23)
      void insert(std::sorted_unique_t s,std::initializer_list<key_type> ilist);
      		 (10)(since C++23)

      Inserts element(s) into the container, if the container does not already contain an element with an equivalent key.

      1) Insertsvalue. Equivalent toreturn emplace(value);.
      2) Insertsvalue. Equivalent toreturn emplace(std::move(value));.
      3) Insertsvalue in the position as close as possible to the position just prior topos. Equivalent toreturn emplace_hint(pos, value);.
      4) Insertsvalue in the position as close as possible to the position just prior topos. Equivalent toreturn emplace_hint(pos, std::move(value));.
      5,7) If*this already contains an element which transparently compares equivalent tox, does nothing. Otherwise, inserts a new element as if by:
      • (5)emplace(pos,std::forward<K>(x)) (in the position as close as possible to the position just prior topos);
      • (7)emplace(std::forward<K>(x)).
      The conversion fromx intokey_type must construct an objectu, for whichfind(k)== find(u) istrue. Otherwise, the behavior is undefined.
      These overloads participate in overload resolution only if
      • The qualified-idCompare::is_transparent is valid and denotes a type, and
      • std::is_constructible_v<value_type, K> istrue,
      which together allows calling this function without constructing an instance ofKey.
      6) Equivalent to the sequence of operations:
      1. Inserts elements from range[first, last) as if byc.insert(c.end(), first, last);.
      2. Sorts the range of newly inserted elements with respect tocompare.
      3. Merges the resulting sorted range and the sorted range of pre-existing elements into a single sorted range. (Note: the merge operation may allocate memory).
      4. Erases all but the first element from each group of consecutive equivalent elements.
      If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pendingLWG2844).
      8) Inserts elements from range[first, last). Equivalent toinsert(first, last);.
      If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pendingLWG2844).
      9) Inserts elements from initializer listilist. Equivalent toinsert(ilist.begin(), ilist.end());.
      If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pendingLWG2844).
      10) Inserts elements from initializer listilist. Equivalent toinsert(s, ilist.begin(), ilist.end());.
      If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pendingLWG2844).
      Information on iterator invalidation is copied fromhere

      Contents

      [edit]Parameters

      pos - iterator to the position before which the new element will be inserted
      value - element value to insert
      first, last - the pair of iterators defining the sourcerange of elements to insert
      ilist - initializer list to insert the values from
      x - a value of any type that can be transparently compared with a key
      s - adisambiguation tag indicating that the input sequence is sorted (with respect tocompare) and contains only unique elements
      Type requirements
      -
      InputIt must meet the requirements ofLegacyInputIterator.

      [edit]Return value

      1,2) A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and abool value set totrue if and only if the insertion took place.
      3-5) An iterator to the inserted element, or to the element that prevented the insertion.
      6) (none)
      7) A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and abool value set totrue if and only if the insertion took place.
      8-10) (none)

      [edit]Exceptions

      1-5,7) If an exception is thrown by any operation, the insertion has no effect.
      This section is incomplete
      Reason: cases 6,8-10

      [edit]Complexity

      1,2) Logarithmic insize(), plus the cost of insertion intoc.
      3-5) Amortized constant if the insertion happens in the position just beforepos, logarithmic insize() otherwise. Plus the cost of insertion intoc.
      6)N+ M·log(M), whereN is thesize() before the operation andM isstd::distance(first, last).
      7) Logarithmic insize(), plus the cost of insertion intoc.
      8) Linear inN, whereN issize() after the operation.
      9)N+ M·log(M), whereN is thesize() before the operation andM isilist.size().
      10) Linear inN, whereN issize() after the operation.

      [edit]Notes

      The hinted insert(3-5)does not return a boolean in order to be signature-compatible with positional insert on sequential containers, such asstd::vector::insert. This makes it possible to create generic inserters such asstd::inserter. One way to check success of a hinted insert is to comparesize() before and after.

      [edit]Example

      Run this code
      #include <cassert>#include <flat_set>#include <iostream> int main(){std::flat_set<int> set; auto result_1= set.insert(3);assert(result_1.first!= set.end());// it is a valid iteratorassert(*result_1.first==3);if(result_1.second)std::cout<<"insert done\n"; auto result_2= set.insert(3);assert(result_2.first== result_1.first);// the same iteratorassert(*result_2.first==3);if(!result_2.second)std::cout<<"no insertion\n";}

      Output:

      insert doneno insertion

      [edit]See also

      constructs element in-place
      (public member function)[edit]
      constructs elements in-place using a hint
      (public member function)[edit]
      creates astd::insert_iterator of type inferred from the argument
      (function template)[edit]
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