all_of function is used to test condition on all the elements in a range[first,last), it will return true if the test condition is true for each and every element in the range or if the range is empty, else it will return false.

Function Prototype

bool all_of (InputIterator first, InputIterator last, UnaryPredicate pred);

About the parameters

first

It is the initial position of the range which is included in the range.

last

It is the last position in the range, which is not included in the range.

pred

It is a unary function which return value which is convertible to bool. This function is used to test condition on the elements in the range.

Sample program using all_of

#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
        int arr_one[] = {2,4,6,8,10};
        int arr_two[] = {2,3,6,8,10};

        if ( all_of(arr_one,arr_one+5,[](int i){return !(i%2);})) {
                cout << "All the elements in the range are even.\n";
        } else {
                cout << "All the elements in the range are not even.\n";
        }

        if ( all_of(arr_two,arr_two+5,[](int i){return !(i%2);})) {
                cout << "All the elements in the range are even.\n";
        } else {
                cout << "All the elements in the range are not even.\n";
        }

        return 0;
}

Output of the program

All the elements in the range are even.
All the elements in the range are not even.

The complexity of all_of function is upto linear