C++ Algorithm Library - includes() Function

---

---

Description

The C++ function std::algorithm::includes() test whether first set is subset of another or not. This member function expects elements in sorted order. It use operator< for comparison.

Declaration

Following is the declaration for std::algorithm::includes() function form std::algorithm header.

C++98

template <class InputIterator1, class InputIterator2>
bool includes(InputIterator1 first1, InputIterator1 last1,
   InputIterator2 first2, InputIterator2 last2);

Parameters

• first1 − Input iterator to the initial position of the first sequence.

• last1 − Input iterator to the final position of the first sequence.

• first2 − Input iterator to the initial position of the second sequence.

• last2 − Input iterator to the final position of the second sequence.

Return value

Returns true if first set is subset of another otherwise returns false.

Exceptions

Throws exception if element comparison or an operation on an iterator throws exception.

Please note that invalid parameters cause undefined behavior.

Time complexity

Linear.

Example

The following example shows the usage of std::algorithm::includes() function.

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main(void) {
   vector<int> v1 = {1, 2, 3, 4, 5};
   vector<int> v2 = {3, 4, 5};
   bool result;

   result = includes(v1.begin(), v1.end(), v2.begin(), v2.end());

   if (result == true)
      cout << "Vector v2 is subset of v1" << endl;

   v2 = {10};

   result = includes(v1.begin(), v1.end(), v2.begin(), v2.end());

   if (result == false)
      cout << "Vector v2 is not subset of v1" << endl;

   return 0;
}

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

Vector v2 is subset of v1
Vector v2 is not subset of v1