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std::set::insert

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Revision as of 07:16, 12 March 2014 by Cubbi (Talk | contribs)

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std::pair<iterator,bool> insert( const value_type& value );
(1)
std::pair<iterator,bool> insert( value_type&& value );
(2) (since C++11)
(3)
iterator insert( iterator hint, const value_type& value );
(until C++11)
iterator insert( const_iterator hint, const value_type& value );
(since C++11)
iterator insert( const_iterator hint, value_type&& value );
(4) (since C++11)
template< class InputIt >
void insert( InputIt first, InputIt last );
(5)
void insert( std::initializer_list<value_type> ilist );
(6) (since C++11)

Inserts element(s) into the container, if the container doesn't already contain an element with an equivalent key.

1-2) inserts value.
3-4) inserts value in the position as close as possible, just prior(since C++11), to hint.
5) Inserts elements from range [first, last).
6) Inserts elements from initializer list ilist.

No iterators or references are invalidated.

Contents

[edit] Parameters

hint - iterator, used as a suggestion as to where to insert the content
value - element value to insert
first, last - range of elements to insert
ilist - initializer list to insert the values from
Type requirements
-
InputIt must meet the requirements of InputIterator.

[edit] Return value

1-2) Returns a pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool denoting whether the insertion took place.
3-4) Returns an iterator to the inserted element, or to the element that prevented the insertion.
5-6) (none)

[edit] Exceptions

1-4) If an exception is thrown by any operation, the insertion has no effect.

[edit] Complexity

1-2) Logarithmic in the size of the container, O(log(size())).
3-4) Amortized constant if the insertion happens in the position just after the hint, logarithmic in the size of the container otherwise.
(until C++11)
3-4) Amortized constant if the insertion happens in the position just before the hint, logarithmic in the size of the container otherwise.
(since C++11)
5-6) O(N*log(size() + N)), where N is the number of elements to insert.

[edit] Notes

The overloads (5-6) are often implemented as a loop that calls the overload (3) with end() as the hint; they are optimized for appending a sorted sequence (such as another set) whose smallest element is greater than the last element in *this

[edit] Example

#include <set>
#include <cassert>
#include <iostream>
 
int main()
{
  std::set<int> set;
 
  auto result_1 = set.insert(3);
  assert(result_1.first != set.end()); // it's a valid iterator
  assert(*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); // same iterator
  assert(*result_2.first == 3);
  if (!result_2.second)
    std::cout << "no insertion\n";
}

Output:

insert done
no insertion

[edit] See also

(C++11)
constructs element in-place
(public member function) [edit]
constructs elements in-place using a hint
(public member function) [edit]