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set::empty() function in C++ STL
C++ STL set::empty() function: Here, we are going to learn about the empty() function of set in C++ STL (Standard Template Library).
Submitted by Radib Kar, on February 16, 2019
C++ STL set::empty() function
set::empty() function is a predefined function, it is used to check whether a set is empty or not. If set is empty it returns true (1), if set is not empty it returns false (0).
Prototype:
set<T> st; //declaration
set<T>::iterator it; //iterator declaration
st.empty( );
Parameter: Nothing to pass
Return type: Bool (True or False)
Usage: The function checks whether the set is empty or not.
Example:
For a set of integer,
set<int> st;
st.insert(4);
st.insert(5);
set content:
4
5
Bool check=st.empty();
check =False
St.erase(st.begin()); //erases 4
St.erase(st.begin()); //erases 5
Set content:
Empty set
//now check again
check=st.empty()
check=TRUE
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";
for(it=st.begin();it!=st.end();it++)
cout<<*it<<" ";
cout<<endl;
}
int main(){
cout<<"Example of empty 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
if(st.empty())
cout<<"It's empty\n";
else
cout<<"It's not empty\n";
cout<<"erasing all elements\n";
st.clear();
if(st.empty())
cout<<"It's empty\n";
else
cout<<"It's not empty\n";
return 0;
}
Output
Example of empty function
inserting 4
inserting 6
inserting 10
Set contents are:
4 6 10
It's not empty
erasing all elements
It's empty