C++ set insert()

C++ set insert() is used for inserting new element in the set.

Because element keys are unique in a set, the insertion operation first checks that whether the given key is already present in the set or not, if the key is present in the set then it is not inserted in the set and the iterator to the existing key is returned otherwise new element is inserted in the set.

Syntax

  single element (1)     pair<iterator,bool> insert (const value_type& val);   //until C++ 11    with hint (2)iterator insert (iterator position, const value_type& val);   //until C++ 11    range (3)  template <class InputIterator>       void insert (InputIterator first, InputIterator last);        //until C++ 11    single element (1)  pair<iterator,bool> insert (const value_type& val);                                  pair<iterator,bool> insert (value_type&& val);           //since C++ 11                with hint (2)iterator insert (const_iterator position, const value_type& val);                            iterator insert (const_iterator position, value_type&& val); //since C++ 11    range (3)template <class InputIterator>                            void insert (InputIterator first, InputIterator last);            //since C++ 11    initializer list (4)       void insert (initializer_list<value_type> il);              //since C++ 11  

Parameter

val: value to insert in the set.

position: Hint for the position to insert element in the set.

first: Beginning of range to insert.

last: End of range to insert.

il: An initializer list.

Return value

Returns a bool pair to indicate whether insertion is happened or not and returns an iterator pointing to the newly inserted element.

Complexity

If a single element is inserted complexity will be logarithmic in size.
If a hint is given and the position given is the optimal then the complexity will be amortized constant.

Iterator validity

No changes.

Data Races

The container is modified.

Exception Safety

This function does not throw exception.

Example 1

Let’s see the simple example to insert the elements into the set:

  #include <iostream>  #include <set>    using namespace std;  int main()  {      set<int> s;         // Function to insert elements      // in the set container      s.insert(1);      s.insert(4);      s.insert(2);      s.insert(5);      s.insert(3);         cout << “The elements in set are: “;      for (auto it = s.begin(); it != s.end(); it++)          cout << *it << ” “;         return 0;  }  

Output:

The elements in set are: 1 2 3 4 5

In the above example, it simply inserts the element with the given key.

Example 2

Let’s see a simple example to insert the element in the specified position:

  #include <iostream>  #include <set>    using namespace std;    int main()  {       set<int> s;         // Function to insert elements      // in the set container      auto itr = s.insert(s.begin(), 1);         // the time taken to insertion      // is very less as the correct      // position for insertion is given      itr = s.insert(itr, 4);      itr = s.insert(itr, 2);      itr = s.insert(itr, 5);      itr = s.insert(itr, 3);         cout << “The elements in set are: “;      for (auto it = s.begin(); it != s.end(); it++)          cout << *it << ” “;         return 0;  }  

Output:

The elements in set are: 1 2 3 4 5

In the above example, elements are inserted in the defined position.

Example 3

Let’s see a simple example to insert the elements of one set to another in a given range:

  #include <iostream>  # include<iostream>  # include<set>    using namespace std;    int main()  {       set<int> s1;         // Function to insert elements      // in the set container      s1.insert(1);      s1.insert(4);      s1.insert(2);      s1.insert(5);      s1.insert(3);         cout << “The elements in set1 are: “;      for (auto it = s1.begin(); it != s1.end(); it++)          cout << *it << ” “;         set<int> s2;         // Function to insert one set to another      // all elements from where 3 is to end is      // inserted to set2      s2.insert(s1.find(3), s1.end());         cout << “nThe elements in set2 are: “;      for (auto it = s2.begin(); it != s2.end(); it++)          cout << *it << ” “;         return 0;  }  

Output:

The elements in set1 are: 1 2 3 4 5   The elements in set2 are: 3 4 5

Example 4

Let’s see a simple example to insert the elements from the initializer list:

  #include <iostream>  #include <set>    using namespace std;    int main(void) {     set<string> m = {“Java”, “C++”, “SQL”};         // Insert the elements from an initializer_list      m.insert({“VB”, “Oracle”});       cout << “Set contains following elements” << endl;       for (auto it = m.begin(); it != m.end(); ++it)        cout << *it<< endl;       return 0;  }  

Output:

Set contains following elements  C++  Java  Oracle  SQL  VB

In the above example, elements are inserted from an initializer list.

Next TopicSet erase() Function

begin()beginners c cbegin()cend()clear()constructor cpp set crbegin()destructor emplace_hint()empty end()function introduction key_comp()max_size()operator professionals swap()tutorial

C++ set insert() Function

C++ set insert()

Syntax

Parameter

Return value

Complexity

Iterator validity

Data Races

Exception Safety

Example 1

Example 2

Example 3

Example 4

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