# Set max_size() function in C++ STL

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In this article we are going to discuss the set::max_size() in C++ STL, their syntax, working and their return values.

## What is Set in C++ STL?

Sets in C++ STL are the containers which must have unique elements in a general order. Sets must have unique elements because the value of the element identifies the element. Once added a value in set container later can’t be modified, although we can still remove or add the values to the set. Sets are used as binary search trees.

## What is set::max_size()?

max_size() is an inbuilt function in C++ STL which is declared in <set> header file. max_size() returns the maximum size of the set container associated with it. In other words, it returns the maximum size that a container can reach, however there is no guarantee it can allocate the elements of that size, it can still fail to allocate the storage to a specific point of a set container.

## Syntax

name_of_set.max_size();

## Parameter

This function accepts no parameter.

## Return value

This function returns the maximum size of the associated set container.

## Example

Input: set<int> myset;
myset.max_size();
Output: size of a set before inserting elements: 461168601842738790

## Example

Live Demo

#include <bits/stdc++.h>
using namespace std;
int main(){
set<int> data_1, data_2;
data_1.insert(100);
cout<<"size of a set after inserting values : "<<data_1.max_size()<< endl;
cout<<"size of a set before inserting values : "<<data_2.max_size();
return 0;
}

## Output

If we run the above code it will generate the following output −

size of a set after inserting values : 461168601842738790
size of a set before inserting values : 461168601842738790

## Example

Live Demo

#include <iostream>
#include <set>
int main (){
int i;
std::set<int> Set;
if(Set.max_size()>1000){
for (i=0; i<=1000; i++)
Set.insert(i);
std::cout<<"There are 1000 elements in a set.";
}
else
std::cout<<"There can't be 1000 elements in a set.";
return 0;
}

## Output

If we run the above code it will generate the following output −

There are 1000 elements in a set.
Updated on 05-Mar-2020 10:35:17