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map::size() function in C++ STL with Example
C++ STL map::size() function with Example: Here, we are going to learn about the map::size() function in C++ STL with an Example.
Submitted by Vivek Kothari, on November 20, 2018
Maps are a part of the C++ STL and key values in maps are generally used to identify the elements i.e. there is a value associated with every key. map::size() is built-in function in C++ used to find the size of the map. The time complexity of this function is constant i.e. O(1).
Syntax:
MapName.size()
Return Value:
It returns the size of the map i.e. number of elements map container have.
Parameters:
There is no parameter to be passed.
Example:
MyMap ={
{1, "c++"},
{2, "java"},
{3, "Python"},
{4, "HTML"},
{5,"PHP"}
};
Here, MyMap.size() returns 5.
Program:
#include <bits/stdc++.h>
using namespace std;
int main()
{
map<int, string> MyMap1, MyMap2;
MyMap1.insert(pair <int, string> (1, "c++"));
MyMap1.insert(pair <int, string> (2, "java"));
MyMap1.insert(pair <int, string> (3, "Python"));
MyMap1.insert(pair <int, string> (4, "HTML"));
MyMap1.insert(pair <int, string> (5, "PHP"));
map <int, string> :: iterator it;
cout<<"Elements in MyMap1 : "<<endl;
for (it = MyMap1.begin(); it != MyMap1.end(); it++)
{
cout <<"key = "<< it->first <<" value = "<< it->second <<endl;
}
cout<<endl;
cout << "size of MyMap1 : " << MyMap1.size()<<endl;
cout << "size of MyMap2 : " << MyMap2.size();
return 0;
}
Output
Elements in MyMap1 :
key = 1 value = c++
key = 2 value = java
key = 3 value = Python
key = 4 value = HTML
key = 5 value = PHP
size of MyMap1 : 5
size of MyMap2 : 0