C++ Map Library - multimap() Function

---

---

Description

The C++ function std::multimap::multimap() constructs a multimap from initialize list.

Declaration

Following is the declaration for std::multimap::multimap() function form std::map header.

C++11

multimap (initializer_list<value_type> il,
          const key_compare& comp = key_compare(),
          const allocator_type& alloc = allocator_type());

Parameters

• il − Initialize list.

• comp − A binary predicate, which takes two key arguments and returns true if first argument goes before second otherwise false. By default it uses less predicate.

• alloc − The allocator object.

Return value

Constructor never return value.

Exceptions

No effect on container if exception is thrown.

Time complexity

Linear i.e. O(n)

Example

The following example shows the usage of std::multimap::multimap() function.

#include <iostream>
#include <map>

using namespace std;

int main(void) {
   /* Multimap with duplicates */
   multimap<char, int> m {
         {'a', 1},
         {'a', 2},
         {'b', 3},
         {'c', 4},
         {'c', 5},
               };

   cout << "Multimap contains following elements:" << endl;

   for (auto it = m.begin(); it != m.end(); ++it)
      cout << it->first << " = " << it->second << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Multimap contains following elements:
a = 1
a = 2
b = 3
c = 4
c = 5