C++ map - size() Function

The C++ map::size function is used to find out the total number of elements in the map.

Note: Map is an ordered data container which implies all its elements are ordered all the time.

Syntax

C++98
C++11

size_type size() const;

size_type size() const noexcept;

Parameters

No parameter is required.

Return Value

Number of elements present in the map.

Time Complexity

Constant i.e, Θ(1).

Example:

In the example below, the map::size function is used find out the total number of elements in a map called MyMap.

#include <iostream>
#include <map>
using namespace std;
 
int main (){
  map<int, string> MyMap;

  MyMap[101] = "John";
  MyMap[102] = "Marry";
  MyMap[103] = "Kim";
  MyMap[104] = "Jo";
  MyMap[105] = "Ramesh";

  cout<<"Map size is: "<<MyMap.size()<<"\n";

  cout<<"Three key/element pairs are added in the Map.\n";
  MyMap[106] = "Suresh";
  MyMap[107] = "Jack";
  MyMap[108] = "Adam";

  cout<<"Now, Map size is: "<<MyMap.size()<<"\n";
  return 0;
}

The output of the above code will be:

Map size is: 5
Three key/element pairs are added in the Map.
Now, Map size is: 8

❮ C++ <map> Library