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set::size() function in C++ STL

C++ STL set::size() function: Here, we are going to learn about the size() function of set in C++ STL (Standard Template Library).
Submitted by Radib Kar, on February 16, 2019

C++ STL set::size() function

set::size() function is a predefined function, it is used to get the size of a set, it returns the total number of elements of the set container.

Syntax

set<T> st; //declaration
set<T>::iterator it; //iterator declaration
int sz=st.size();

Parameter(s)

This function does not accept any parameter.

Return value

This function returns size of the set.

Sample Input and Output

For a set of integer,
set<int> st;
set<int>::iterator it;

st.insert(4);
st.insert(5);

set content:
    4
    5

int sz=st.size(); //sz=size of set that is 2
Print sz; //prints 2

Header file

Header file to be included:

#include <iostream>
#include <set>
OR
#include <bits/stdc++.h>

Example

#include <bits/stdc++.h>
using namespace std;

void printSet(set<int> st){
    set<int>:: iterator it;
    cout<<"Set contents are:\n";
    for(it=st.begin();it!=st.end();it++)
    cout<<*it<<" ";
    cout<<endl;
    
}

int main(){
    cout<<"Example of size function\n";
    set<int> st;
    set<int>:: iterator it;
    cout<<"inserting 4\n";
    st.insert(4);
    cout<<"inserting 6\n";
    st.insert(6);
    cout<<"inserting 10\n";
    st.insert(10);
    
    printSet(st); //printing current set
    
    //finding set sizeof
    
    cout<<"current set size is: "<<st.size();
    
    return 0;
}

Output

Example of size function
inserting 4      
inserting 6      
inserting 10     
Set contents are:
4 6 10  
current set size is: 3