C++ Map Library - insert() Function


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Description

The C++ function std::map::insert() extends map by inserting new element. This function increases container size by one.

Declaration

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

C++11

template <class P>
iterator insert (const_iterator position, P&& val);

Parameters

  • position − Hint for the position to insert element.

  • val − value to be inserted.

Return value

Returns an iterator pointing to the newly inserted element.

Exceptions

This member function doesn't throw exception.

Time complexity

Logarithmic i.e. O(log n).

Example

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

#include <iostream>
#include <map>

using namespace std;

int main(void) {
   map<char, int> m = {
            {'b', 2},
            {'c', 3},
            {'d', 4},
            };

   m.insert(m.begin(), move(pair<char, int>('a', 1)));
   m.insert(m.end(), move(pair<char, int>('e', 5)));

   cout << "Map 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 −

Map contains following elements
a = 1
b = 2
c = 3
d = 4
e = 5
map.htm
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