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× C++ Standard Library C++ STL Library


The C++ vector::operator== function is used to check whether two vectors are equal or not. It returns true if two vectors are equal, else returns false. vector::operator== checks the size of both vectors, if sizes are same then it compares elements of vectors sequentially and stops comparison after first mismatch.

Syntax

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

Parameters

lhs First vector.
rhs Second vector.

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 vector::operator== function is used to check whether two vectors are equal or not.

#include <iostream>
#include <vector>
using namespace std;
 
int main (){
  vector<int> vec1 {10, 20, 30};
  vector<int> vec2 {10, 20, 30};
  vector<int> vec3 {10, 20};

  if (vec1 == vec2)
    cout<<"vec1 and vec2 are equal.\n";
  else
    cout<<"vec1 and vec2 are not equal.\n";

  if (vec1 == vec3)
    cout<<"vec1 and vec3 are equal.\n";
  else
    cout<<"vec1 and vec3 are not equal.\n";
    
  return 0;
}

The output of the above code will be:

vec1 and vec2 are equal.
vec1 and vec3 are not equal.

❮ C++ - Vector