std::find, std::find_if, std::find_if_not

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Defined in header `<algorithm>`

template< class InputIterator, class T > InputIterator find( InputIterator first, InputIterator last, const T& value );	(1)

template< class InputIterator, class UnaryPredicate > InputIterator find_if( InputIterator first, InputIterator last, UnaryPredicate p );	(2)

template< class InputIterator, class UnaryPredicator > InputIterator find_if_not( InputIterator first, InputIterator last, UnaryPredicator q );	(3)	(C++11 feature)

Finds the first element in the range [first, last) satisfying specific criteria. The first version searches for element, equal to value, the second version searches for element for which predicate p returns true, the third version searches for element for which predicate q returns false.

First version:

template<class InputIterator, class T> InputIterator find(InputIterator first, InputIterator last, const T& value) { for (; first != last; ++first) { if (*first == value) { return first; } } return last; }
Second version:
template< class InputIterator, class UnaryPredicate > InputIterator find(InputIterator first, InputIterator last, UnaryPredicate p) { for (; first != last; ++first) { if (p(*first)) return first; } return last; }
Third version:
template< class InputIterator, class BinaryPredicator > InputIterator find(InputIterator first, InputIterator last, BinaryPredicator p) { for (; first != last; ++first) { if (!p(*first)) return first; } return last; }

[edit] Example

The following code uses find to search a vector of integers for the number 3:

int num_to_find = 3;
 
std::vector<int> v1;
for (int i = 0; i < 10; i++) {
    v1.push_back(i);
}
 
std::vector<int>::iterator result;
result = find(v1.begin(), v1.end(), num_to_find);
 
if (result == v1.end()) {
    std::cout << "did not find a match for: " << num_to_find;
} else {
    std::cout << "match: " << *result;
}