std::equal() in C++

11 Jun, 2022
std::equal() helps to compares the elements within the range [first_1,last_1) with those within range beginning at first_2. Syntax 1:
template 
  bool equal (InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2)
    
first_1, last_1 : Initial and final positions of the first
    sequence. All the elements are present within a range [first_1,last_1)
first2 : Initial position of the second sequence.

Returns : 
true, if all of the elements in both ranges match; otherwise false
CPP
// C++ program illustrating// use of  bool equal (InputIterator1 first1, InputIterator1 last1,// InputIterator2 first2)      #include <bits/stdc++.h> int main(){    int v1[] = { 10, 20, 30, 40, 50 };    std::vector<int> vector_1 (v1, v1 + sizeof(v1) / sizeof(int) );     // Printing vector1    std::cout << "Vector contains : ";    for (unsigned int i = 0; i < vector_1.size(); i++)        std::cout << " " << vector_1[i];    std::cout << "\n";     // using std::equal()    // Comparison within default constructor    if ( std::equal (vector_1.begin(), vector_1.end(), v1) )        std::cout << "The contents of both sequences are equal.\n";    else        printf("The contents of both sequences differ."); }
Output:
Vector contains :  10, 20, 30, 40, 50
The contents of both sequences are equal.
Syntax 2:
template 
  bool equal (InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2, BinaryPredicate pred);

first_1, last_1 : Initial and final positions of the first
    sequence. All the elements are present within a range [first_1,last_1)
first2 : Initial position of the second sequence.
pred : Binary function that accepts two elements as argument 
      and returns a value convertible to boolean.

Returns : 
true, if all of the elements in both ranges match; otherwise false
CPP
// C++ program illustrating// use of bool equal (InputIterator1 first1, InputIterator1 last1,// InputIterator2 first2, BinaryPredicate pred); #include <bits/stdc++.h> bool pred(int i, int j){    return (i != j);} int main(){    int v1[] = { 10, 20, 30, 40, 50 };    std::vector<int> vector_1 (v1, v1 + sizeof(v1) / sizeof(int) );     // Printing vector1    std::cout << "Vector contains : ";    for (unsigned int i = 0; i < vector_1.size(); i++)        std::cout << " " << vector_1[i];    std::cout << "\n";     // using std::equal()    // Comparison based on pred    if ( std::equal (vector_1.begin(), vector_1.end(), v1, pred) )        std::cout << "The contents of both sequences are equal.\n";    else        printf("The contents of both sequences differ."); }
Output:
Vector contains :  10, 20, 30, 40, 50
The contents of both sequences differ.
Time complexity: O(n)
Related Articles:
std::max_element
std::max
std::min
std::min_element in C++
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