std::find_first_of

From Cppreference

Jump to: navigation, search
Defined in header <algorithm>

template< class ForwardIterator1, class ForwardIterator2 >

ForwardIterator1 find_first_of( ForwardIterator1 first, ForwardIterator1 last,

                                ForwardIterator2 s_first, ForwardIterator2 s_last );
(1)
template< class ForwardIterator1, class ForwardIterator2, class BinaryPredicate >

ForwardIterator1 find_first_of( ForwardIterator1 first, ForwardIterator1 last,

                                ForwardIterator2 s_first, ForwardIterator2 s_last, BinaryPredicate p );
(2)

Searches the range [first, last) for any of the elements in the range [s_first, s_last). The first version uses operator== to compare the elements, the second version uses the given binary predicate p.

Contents

[edit] Parameters

first, last - the range of elements to examine
s_first, s_last - the range of elements to search for
p - binary predicate which returns ​true if the elements should be treated as equal.

The signature of the predicate function should be equivalent to the following:

bool pred(const Type1 &a, const Type2 &b);

The signature does not need to have const &, but the function must not modify the objects passed to it.
The types Type1 and Type2 must be such that objects of types ForwardIterator1 and ForwardIterator2 can be dereferenced and then implicitly converted to Type1 and Type2 respectively.

[edit] Return value

iterator to the first element in the range [first, last) that is equal to an element from the range [s_first; s_last). If no such element is found, last is returned.

[edit] Complexity

does at most (S*N) comparisons where S = distance(s_first, s_last) and N = distance(first, last).

[edit] Equivalent function

[edit] Example

The following code searches for any of specified integers in a vector of integers:

#include <algorithm>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v{0, 1, 2, 3, 4, 5};
    std::vector<int> t{3, 19, 2};
 
    auto result = std::find_first_of(v.begin(), v.end(), t.begin(), t.end());
 
    if (*result == v.end()) {
        std::cout << "any of {3, 19, 2} not found";
    } else {
        std::cout << "found a match at "
                  << std::distance(v.begin(), result) << "\n";
    }
 }

Output:

found a match at 2

[edit] See also

find
find_if
find_if_not


(C++11)
finds the first element satisfying specific criteria
(function template)