Comparator in vector C++

I am trying to solve a simple solution for comparing 2 vectors in this post in C++. Let us use STL vectors and std:: equal function to compare. 
There are different ways the comparison can be achieved. 

1. Using the == operator


Example : 

vector<int> first = {2,4,6,8,10};
vector<int> second = {2,4,6,8,10};

Comparing them can be done using ‘==’ operator as follows: 


if (first == second){    std::cout << “The vectors are same” << std::endl;}





The problems with == are 
a. It cannot use custom comparators
b. Cannot compare sub-vector groups 

2. std:: equal can be used to compare 

for equality: 

bool equal (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2);

for predicate: 



bool equal (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, BinaryPredicate pred);





Equality can be used to compare sub vectors: 
Example: 
Comparing all elements can be done by using 


bool isEqual = std::equal(first.begin(),first.end(),second.begin());





Comparing the subset of elements the following can be done.


vector<int> a = {1,2,3,4,5,6};
vector<int> b = {4,5,6}; 


bool isEqual = std::equal( b.begin(),b.end(), a.begin()+2);
if(isEqual)
{
    cout<<"The vectors are equal"<<endl;
}



















































 






We can use custom comparators. Let’s see how we can do it. 


vector<string> first ={"this", "is", "a", "practise", "of","custom", "comparators"};
vector<string> second ={"THIS", "IS", "A", "PRACTISE", "OF","CUSTOM", "COMPARATORS"};
std::function< bool (const string &, const string & )> comparator = [](const string &left, const string &right)
{
    return std::equal(left.begin(),left.end(),right.begin(),[](const char &l,const char &r){ return ::toupper(l)==::toupper(r))});
}
bool isEqual = std::equal(first.begin(),first.end(),second.begin(),comparator);
if(isEqual)
    cout<<"The strings are same"<<endl; 
else
    cout<<"The strings are not same"<<endl; 




















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