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× C++ Standard Library C++ STL Library


The C++ list::operator== function is used to check whether two lists are equal or not. It returns true if two lists are equal, else returns false. list::operator== compares elements of lists sequentially and stops comparison after first mismatch.

Syntax

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

Parameters

lhs First list.
rhs Second list.

Return Value

Returns true if the contents of lhs are equal to the contents of rhs, else returns false.

Time Complexity

Linear i.e, Θ(n).

Example:

In the below example, the list::operator== function is used to check whether two lists are equal or not.

#include <iostream>
#include <list>
using namespace std;
 
int main (){
  list<int> list1 {10, 20, 30};
  list<int> list2 {10, 20, 30};
  list<int> list3 {10, 20};

  if (list1 == list2)
    cout<<"list1 and list2 are equal.\n";
  else
    cout<<"list1 and list2 are not equal.\n";

  if (list1 == list3)
    cout<<"list1 and list3 are equal.\n";
  else
    cout<<"list1 and list3 are not equal.\n";
    
  return 0;
}

The output of the above code will be:

list1 and list2 are equal.
list1 and list3 are not equal.

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