C++ Unordered_set Library - operators

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Description

These are relational operators for unordered_set.

Declaration

Following is the declaration for std::operators(unordered_set).

C++11

template <class Key, class Hash, class Pred, class Alloc>
  bool operator== ( const unordered_set<Key,Hash,Pred,Alloc>& lhs,
                    const unordered_set<Key,Hash,Pred,Alloc>& rhs );

Parameters

lhs, rhs − unorder list containers.

Return value

It returns true if the condition holds, and false otherwise.

Exceptions

Exception is thrown if any element comparison object throws exception.

Please note that invalid arguments cause undefined behavior.

Time complexity

constant time.

Example

The following example shows the usage of std::operators.

#include <iostream>
#include <string>
#include <unordered_set>

int main () {
   std::unordered_set<std::string>
      a = {"goole","yahoo","verizon"},
      b = {"goole","verizon","yahoo"},
      c = {"verizon","goole","yahoo","oracle"};

   if (a==b) std::cout << "a and b are equal\n";
   if (b!=c) std::cout << "b and c are not equal\n";

   return 0;
}

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

a and b are equal
b and c are not equal