C++ Unordered_map Library - insert() Function

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Description

The C++ function std::unordered_map::insert() extends map by inserting new element from initializer list. This member function increases container size.

Declaration

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

C++11

void insert(initializer_list<value_type> il);

Parameters

il − Initializer list.

Return value

None

Time complexity

Linear i.e. O(n) in average case.

Quadratic i.e. O(N * (size+ 1)) in worst case.

Example

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

#include <iostream>
#include <unordered_map>

using namespace std;

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

   um.insert({{'a', 1}, {'e', 5}});

   cout << "Unordered map contains following elements" << endl;

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

   return 0;
}

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

Unordered map contains following elements
e = 5
a = 1
d = 4
b = 2
c = 3