=====insert=====
Syntax:

<code>
    #include <vector>
    iterator insert( iterator loc, const TYPE& val );
    void insert( iterator loc, size_type num, const TYPE& val );
    void insert( iterator loc, input_iterator start, input_iterator end );
</code>

The insert method 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''.

Note that inserting elements into a vector can be relatively time-intensive,
since the underlying data structure for a vector is an array. In order to
insert data into an array, you might need to displace a lot of the elements of
that array, and this can take [[/complexity|linear time]]. If you are planning on doing a lot
of insertions into your vector and you care about speed, you might be better
off using a container that has a linked list as its underlying data structure
(such as a [[stl/list/|list]] or a [[stl/deque/start/|deque]]).

For example, the following code uses the insert() function to splice four
copies of the character 'C' into a vector of characters:

<code>
   // 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 + 'A' );
   }

   // 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;
   }
</code>

This code would display:

<code terminal>
   CCCCABCDEFGHIJ
</code>

Here is another example of the insert method. In this code, insert is
used to append the contents of one vector into the end of another:

<code>
    vector<int> v1;
    v1.push_back( 0 );
    v1.push_back( 1 );
    v1.push_back( 2 );
    v1.push_back( 3 );

    vector<int> v2;
    v2.push_back( 5 );
    v2.push_back( 6 );
    v2.push_back( 7 );
    v2.push_back( 8 );

    cout << "Before, v2 is: ";
    for( vector<int>::size_type i = 0; i < v2.size(); i++ ) {
      cout << v2[i] << " ";
    }
    cout << endl;

    v2.insert( v2.end(), v1.begin(), v1.end() );

    cout << "After, v2 is: ";
    for( vector<int>::size_type i = 0; i < v2.size(); i++ ) {
      cout << v2[i] << " ";
    }
    cout << endl;
</code>

When run, this code displays:

<code terminal>
    Before, v2 is: 5 6 7 8
    After, v2 is: 5 6 7 8 0 1 2 3
</code>

Related Topics: [[assign]], [[erase]], [[push_back]], [[insert]]