C++ Algorithm Library - any_of() Function

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Description

The C++ function std::algorithm::any_of() Returns true if predicate returns true for any of the elements in the range of first to last. If range is empty then also true is returned otherwise it returns false.

Declaration

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

C++11

template <class InputIterator, class UnaryPredicate>
bool any_of (InputIterator first, InputIterator last, UnaryPredicate pred);

Parameters

• first − Input iterators to the initial positions in a sequence.

• last − Input iterators to the final positions in a sequence.

• pred − An unary predicate function that accepts an element and returns a bool.

Return value

Returns true if predicate returns true for any of the elements in the range or if the range is empty otherwise returns false.

Exceptions

Throws exception if either predicate or an operation on an iterator throws exception.

Please note that invalid parameters cause undefined behavior.

Time complexity

Linear in the distance between first and last.

Example

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

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

using namespace std;

bool is_odd(int n) {
   return (n % 2 != 0);
}

int main(void) {
   vector<int> v = {2, 4, 6, 8, 11};
   bool result;

   result = any_of(v.begin(), v.end(), is_odd);

   if (result == true)
      cout << "Vector contains at least one odd number." << endl;

   v[4] = 10;

   result = any_of(v.begin(), v.end(), is_odd);

   if (result == false)
      cout << "Vector contains all even number." << endl;

   return 0;
}

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

Vector contains at least one odd number.
Vector contains all even number.