boost::algorithm::one_of() in C++ library

Last Updated : 30 May, 2019

The one_of() function in C++ boost library is found under the header 'boost/algorithm/cxx11/one_of.hpp' which tests the elements of a sequence and returns true if exactly one of the element share the property given. It takes a sequence and a predicate, and returns true if the predicate returns true for exactly one given element in the sequence. Syntax:

bool one_of ( InputIterator first, InputIterator last, Predicate p ) or bool one_of ( const Range &R, Predicate p)

Parameters: The function accepts parameters as described below:

first: It specifies the input iterators to the initial positions in a sequence.
second: It specifies the input iterators to the final positions in a sequence.
p: It specifies a unary predicate function that accepts an element and returns a bool.
R: It is the complete sequence.

Return Value: The function returns true if the given predicate is true on exactly one of the element of the sequence, else it returns false. Below is the implementation of the above approach: Program-1:

// C++ program to implement the
// above mentioned function

#include <bits/stdc++.h>
#include <boost/algorithm/cxx11/one_of.hpp>
using namespace std;
// using boost::algorithm;

// Predicate function to check if
// the element is odd or not
bool isOdd(int i)
{
    return i % 2 == 1;
}

// Drivers code
int main()
{

    // Declares the sequence
    int c[] = { 1, 2, 3 };

    // Run the function with second syntax
    bool ans
        = boost::algorithm::one_of(c, isOdd);

    // Condition to check
    if (ans == 1)
        cout << "Exactly one element is odd";
    else
        cout << "Exactly one element is not odd";
    return 0;
}

Output:

Exactly one element is not odd

Program-2:

// C++ program to implement the
// above mentioned function

#include <bits/stdc++.h>
#include <boost/algorithm/cxx11/one_of.hpp>
using namespace std;
// using boost::algorithm;

// Predicate function to check if
// the elements are less than 7 or not
bool oneLessThanSeven(int i)
{
    return i < 7;
}

// Drivers code
int main()
{

    // Declares the sequence
    int a[] = { 1, 9, 10, 8 };

    // Run the function with first syntax
    bool ans
        = boost::algorithm::one_of(a, a + 4,
                                   oneLessThanSeven);

    // Condition to check
    if (ans == 1)
        cout << "Exactly one element is less than 7";
    else
        cout << "Exactly one element is not less than 7";
    return 0;
}