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

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

C++ STL set::emplace() function

set::emplace() function is a predefined function, it is used to insert a new element to the set, if element is unique.

Prototype:

    set<T> st; //declaration
    st.emplace(T item);

Parameter: T item; //T is the data type

Return type: If it successfully inserts then it returns a pair<Iterator pointer to the inserted value, True>, Else It returns a pair<iterator to the existing value in the set, False>

Usage: The function inserts unique elements to the set.

Example:

    For a set of integer,
    set<int> st;
    st.emplace(5);
    st.emplace(4);
    set content: //sorted always(ordered)
        4
        5

    st.emplace(5) //no insertion this time
    set content: 
        4
        5

Header file to be included:

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

C++ implementation:

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

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

int main(){
	cout<<"Example of emplace function\n";
	set<int> st;
	set<int>:: iterator it;
	cout<<"inserting 4\n";
	st.emplace(4);
	cout<<"inserting 6\n";
	st.emplace(6);
	cout<<"inserting 10\n";
	st.emplace(10);

	printSet(st); //printing current set
	
	return 0;
}

Output

Example of emplace function
inserting 4
inserting 6
inserting 10
Set contents are:
4 6 10