std::find, std::find_if, std::find_if_not
From Cppreference
| Defined in header
<algorithm> | ||
| template< class InputIterator, class T >
InputIterator find( InputIterator first, InputIterator last, | (1) | |
| template< class InputIterator, class UnaryPredicate >
InputIterator find_if( InputIterator first, InputIterator last, | (2) | |
| template< class InputIterator, class UnaryPredicator >
InputIterator find_if_not( InputIterator first, InputIterator last, | (3) | (C++0x 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.
Contents |
Parameters
| first, last | - | the range of elements to examine | |||||||||
| value | - | value to compare the elements to | |||||||||
| p | - | unary predicate which returns true for the required element. The signature of the predicate function should be equivalent to the following:
The signature does not need to have const &, but the function must not modify the objects passed to it. | |||||||||
| q | - | unary predicate which returns false for the required element. The signature of the predicate function should be equivalent to the following:
The signature does not need to have const &, but the function must not modify the objects passed to it. | |||||||||
Return value
iterator to the first element satisfying the condition or last if no such element is found.
Complexity
linear in the distance between first and last
Equivalent function
| 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; } |
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; }
Output:
match: 3
See also
| finds two identical (or some other relationship) items adjacent to each other (function template) | |
| finds the last sequence of elements in a certain range (function template) | |
| searches for any one of a set of elements (function template) | |
| finds the first position where two ranges differ (function template) | |
| searches for a range of elements (function template) | |
