C++ set operator less than=

C++ set operator less than= with tutorial for beginners and professionals with examples on constructor, destructor, operator=(), begin(), cbegin(), cend(), end(), crbegin(), empty(), max_size(), clear(), emplace_hint(), key_comp(), swap() etc.

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C++ std operator<=

C++ std Operator<= is a non-member overloaded function of set in C++. This function is used to check whether the first set is less than or equal to other or not.

Note: Operator <= compares element sequentially and at first mismatch comparison will stop.

Syntax

template <class T, class Compare, class Alloc>
  bool operator<= ( const set<T,Compare,Alloc>& lhs,
                    const set<T,Compare,Alloc>& rhs );

Parameter

lhs: First set object.

rhs: Second set object.

Return value

It returns true if the left side of the set object is less than or equal to the right side of the set object otherwise false.

Complexity

Complexity will be constant, if the size of lhs and rhs is different.

Otherwise, up to linear in the size of lhs and rhs.

Iterator validity

No changes.

Data Races

Containers, lhs and rhs are accessed.

Concurrently accessing the elements of unmodified set is always safe.

Exception Safety

This function does not throw an exception.

Example 1

Let's see the simple example to check whether the first set is less than or equal to or not:

#include <iostream>
#include <set>

using namespace std;

int main() {
   set<char> m1;
   set<char> m2;

   m1.emplace('a');
   m2.emplace('a');

   if (m1 <= m2)
      cout << "Set m1 is less than or equal to m2." << endl;

   m1.emplace('b');

   if (!(m1 <= m2))
      cout << "Set m1 is not less than or equal to m2." << endl;

   return 0;
}

Output:

Set m1 is less than or equal to m2.
Set m1 is not less than or equal to m2.

In the above example, there are two sets m1 and m2. m1 and m2 contains one element. When we compare both sets then it will display the message "set m1 is less than or equal to m2" and after adding one extra element in m1 then it will display the message that "set m1 is not less than or equal to m2".

Example 2

Let's see a simple example:

#include <set>  
#include <iostream>  
  
int main ()  
{  
   using namespace std;  
   set <int> m1, m2, m3, m4;  
   int i;  
  
   for (i = 1; i <3; i ++)  
   {  
      m1.insert (i);  
      m2.insert (i * i);  
      m3.insert ( i - 1);  
      m4.insert (i);  
   }  
  
   if (m1 <= m2)  
      cout << "The set m1 is less than or equal to the set m2." << endl;  
   else  
      cout << "The set m1 is greater than the set m2." << endl;  
  
   if (m1 <= m3)  
      cout << "The set m1 is less than or equal to the set m3." << endl;  
   else  
      cout << "The set m1 is greater than the set m3." << endl;  
  
   if (m1 <= m4)  
      cout << "The set m1 is less than or equal to the set m4." << endl;  
   else  
      cout << "The set m1 is greater than the set m4." << endl;  
}

Output:

The set m1 is less than or equal to the set m2.
The set m1 is greater than the set m3.
The set m1 is less than or equal to the set m4.

Example 3

Let's see a simple example:

#include <iostream>
 #include <set>
 
 using namespace std;

int  main () 
{ 
  set < int >  s1 ,  s2 ; 
  s1 . insert ( 10 ); 
  s1 . insert ( 20 ); 
  s1 . insert ( 30 ); 
  s2  =  s1 ;

  cout  <<  ( s1  <=  s2 )  << endl ;

  s1 . insert ( 40 );

  cout  <<  ( s1  <=  s2 )  << endl ; 
}

Output:

1
0

In the above example, if set s1 is less than or equal to s2 then it will return 1 otherwise, 0.

Example 4

#include <set>  
#include <iostream>  
using namespace std; 
  
int main ()  
{  
   set<string> m2;
   typedef set<string> login; 
   
   m2.insert("xyz@123") ; //stored password
   
   string password;
   login m1;
   
       cout<<"---------Login----------"<<endl<<endl;
       cout<<"Enter password: \n";
       cin>> password;       // Get value
       m1.insert(password);   // Put them in set

     cout<<"Password you have entered: \n";
     for (auto it = m1.begin(); it != m1.end(); it++) {
        cout << (*it)<< endl;
      }
      cout<<"Password stored in the system :\n";
     for (auto it = m2.begin(); it != m2.end(); it++) {
        cout << (*it)<< endl;
     }
  
   if (m2 <= m1)  
        cout << "\nWelcome to your Page..." << endl; 
   else  
        cout << "\nIncorrect Password..." << endl; 
      
      return 0;
}

Output:

1).
---------Login----------

Enter password: 
[email protected]
Password you have entered: 
[email protected]
Password stored in the system :
[email protected]

Welcome to your Page...

2).
---------Login----------

Enter password: 
[email protected]
Password you have entered: 
[email protected]
Password stored in the system:
[email protected]

Incorrect Password...

In the above example, there are two sets m1 and m2. m1 contains stored password and second set m2 stores user's entered password. It checks whether the m2 is less than or equal to m1 or not. If password of m2 is less than or equal to m1 then login is successful otherwise login fails.

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C++ set operator less than=

C++ std operator<=

Note: Operator <= compares element sequentially and at first mismatch comparison will stop.

Syntax

Parameter

Return value

Complexity

Iterator validity

Data Races

Exception Safety

Example 1

Example 2

Example 3

Example 4

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