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find_first_of
function template
<algorithm>
template <class ForwardIterator1, class ForwardIterator2>
ForwardIterator1 find_first_of ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2 );
template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
ForwardIterator1 find_first_of ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred );
Find element from set in range
Returns an interator to the first occurrence in the range [first1,last1) of any of the elements in [first2,last2).
All the elements in [first2,last2) are compared to the each of the values in [first,last) until a match is found. The comparison is performed by either applying the == operator, or the template parameter comp (for the second version).
The behavior of this function template is equivalent to:
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template<class ForwardIterator1, class ForwardIterator2>
ForwardIterator1 find_first_of ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2)
{
for ( ; first1 != last1; ++first1 )
for (ForwardIterator2 it=first2; it!=last2; ++it)
if (*it==*first1) // or: if (comp(*it,*first)) for the pred version
return first1;
return last1;
}
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Parameters
- first1, last1
- Forward iterators to the initial and final positions of the searched sequence. The range used is [first1,last1), which contains all the elements between first1 and last1, including the element pointed by first1 but not the element pointed by last1.
- first2, last2
- Forward iterators to the initial and final positions of the element values to be searched for. The range used is [first2,last2).
- pred
- Binary predicate taking two elements as argument, and returning the result of the comparison between them, with true (non-zero) meaning that they are to be considered equal, and false (zero) that they are not-equal. This can either be a pointer to a function or an object whose class overloads operator().
Return value
An iterator to the first element in [first1,last1) that is part of [first2,last2).
If none of the elements is found, the function returns last1.
Example
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// find_first_of example
#include <iostream>
#include <algorithm>
#include <cctype>
#include <vector>
using namespace std;
bool comp_case_insensitive (char c1, char c2) {
return (tolower(c1)==tolower(c2));
}
int main () {
int mychars[] = {'a','b','c','A','B','C'};
vector<char> myvector (mychars,mychars+6);
vector<char>::iterator it;
int match[] = {'A','B','C'};
// using default comparison:
it = find_first_of (myvector.begin(), myvector.end(), match, match+3);
if (it!=myvector.end())
cout << "first match is: " << *it << endl;
// using predicate comparison:
it = find_first_of (myvector.begin(), myvector.end(),
match, match+3, comp_case_insensitive);
if (it!=myvector.end())
cout << "first match is: " << *it << endl;
return 0;
}
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Output:
First match is: A
First match is: a
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Complexity
At most, performs count1*count2 comparisons or applications of pred (where countX is the distance between firstX and lastX).
See also
| search | Find subsequence in range (function template) |
| find | Find value in range (function template) |
| find_if | Find element in range (function template) |
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