C++ Map Library - operator<= Function


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Description

The C++ function std::map::operator<= tests whether first map is less than or equal to other or not.

Operator <= compares element sequentially and comparison stops at first mismatch.

Declaration

Following is the declaration for std::map::operator<= function form std::map header.

C++98

template <class Key, class T, class Compare, class Alloc>
bool operator<= ( const map<Key,T,Compare,Alloc>& m1,
                  const map<Key,T,Compare,Alloc>& m2);

Parameters

  • m1 − First map object.

  • m2 − Second map object.

Return value

Returns true if first map is less than or equal to second otherwise false.

Exceptions

This function doesn't throw exception.

Time complexity

Linear i.e. O(n)

Example

The following example shows the usage of std::map::operator<= function.

Live Demo
#include <iostream>
#include <map>

using namespace std;

int main(void) {
   map<char, int> m1;
   map<char, int> m2;

   m1.emplace('a', 1);
   m2.emplace('a', 1);

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

   m1.emplace('b', 2);

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

   return 0;
}

Let us compile and run the above program, this will produce the following result −

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

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