C++ multimap begin() function

The C++ multimap begin()function is used to return an iterator referring to the first element of the multimap container.

Syntax

Parameter

None

Return value

It returns an iterator pointing to the first element of the multimap.

Complexity

Constant.

Iterator validity

No changes.

Data Races

The container is accessed. Neither the constant nor the non-constant versions modify the container.

Exception Safety

This function never throws exception.

Example 1

Let's see the simple example for begin() function:

Output:

a => Java
a => Android
b => C++
b => Python

In the above example, begin()function is used to return an iterator pointing to the first element in the mymultimap multimap.

Example 2

Let's see a simple example to iterate over the multimap using for-each loop:

Output:

Room1 = 100
Room1 = 300
Room1 = 100
Room2 = 200

In the above example, we are using an STL algorithm for-each to iterate over the multimap. It will iterate on each of the multimap element and call the callback provided by us.

Example 3

Let's see a simple example to iterate over the multimap using while loop:

Output:

Elements are: 
100 = Nikita
100 = Aman
200 = Deep
200 = Suman
300 = Priya

In the above, begin()function is used to return an iterator pointing to the first element in the mymultimap multimap.

Example 4

Let's see a simple example:

Output:

The first element of m1 is 0
First element of m1 is now 1

In the above example, begin() function is used to return an iterator pointing to the first element in the mymultimap multimap.