function template
std::find_end
<algorithm>
template <class ForwardIterator1, class ForwardIterator2>
ForwardIterator1 find_end ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2 );
template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
ForwardIterator1 find_end ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred );
Find last subsequence in range
Searches the range
[first1,last1) for the last occurrence of the sequence defined by
[first2,last2), and returns an iterator to its first element.
The sequence of elements in
[first2,last2) is compared to the possible subsequences of successive elements within
[first1,last1) by either applying the
== comparison operator to each element, 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_end ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2)
{
if (first2==last2) return last1; // specified in C++11
ForwardIterator1 ret = last1;
while (first1!=last1)
{
ForwardIterator1 it1 = first1;
ForwardIterator2 it2 = first2;
while (*it1==*it2) { // or: while (pred(*it1,*it2)) for the pred version
++it1; ++it2;
if (it2==last2) { ret=first1; break; }
if (it1==last1) return ret;
}
++first1;
}
return ret;
}
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A similar algorithm function, but returning the first occurrence instead of the last, is
search.
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 sequence to be searched for. The range used is [first2,last2).
- pred
- Binary predicate taking two elements as argument (one of each of the two sequences), 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 of the last occurrence of the sequence
[first2,last2) in
[first1,last1).
If the sequence is not found, the function returns
last1.
Example
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// find_end example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
bool myfunction (int i, int j) {
return (i==j);
}
int main () {
int myints[] = {1,2,3,4,5,1,2,3,4,5};
vector<int> myvector (myints,myints+10);
vector<int>::iterator it;
int match1[] = {1,2,3};
// using default comparison:
it = find_end (myvector.begin(), myvector.end(), match1, match1+3);
if (it!=myvector.end())
cout << "match1 last found at position " << int(it-myvector.begin()) << endl;
int match2[] = {4,5,1};
// using predicate comparison:
it = find_end (myvector.begin(), myvector.end(), match2, match2+3, myfunction);
if (it!=myvector.end())
cout << "match2 last found at position " << int(it-myvector.begin()) << endl;
return 0;
}
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Output:
Match found at position 5
Match found at position 3
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Complexity
At most, performs
count2*(1+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)