cppreference.com > C++ Lists > insert insert Syntax:
      #include <list>
      iterator insert( iterator loc, const TYPE& val );
      void insert( iterator loc, size_type num, const TYPE& val );
      template<TYPE> void insert( iterator loc, input_iterator start, input_iterator end );
The insert() function either: inserts val before loc, returning an iterator to the element inserted, inserts num copies of val before loc, or inserts the elements from start to end before loc. For example:
     // Create a vector, load it with the first 10 characters of the alphabet
     vector<char> alphaVector;
     for( int i=0; i < 10; i++ ) {
       alphaVector.push_back( i + 65 );
     }

     // Insert four C's into the vector
     vector<char>::iterator theIterator = alphaVector.begin();
     alphaVector.insert( theIterator, 4, 'C' );

     // Display the vector
     for( theIterator = alphaVector.begin(); theIterator != alphaVector.end(); theIterator++ )    {
       cout << *theIterator;
     }
This code would display:
     CCCCABCDEFGHIJ
Related topics: assign erase merge push_back push_front splice