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std::find_end

From cppreference.com
 
 
 
Defined in header <algorithm>
template< class ForwardIterator1, class ForwardIterator2 >

ForwardIterator1 find_end( ForwardIterator1 first, ForwardIterator1 last,

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

ForwardIterator1 find_end( ForwardIterator1 first, ForwardIterator1 last,

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

Searches for the last subsequence of elements [s_first, s_last) in the range [first, 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 beginning of last subsequence [s_first, s_last) in range [first, last).
If no such subsequence is found, last is returned. (until C++11)
If [s_first, s_last) is empty or if no such subsequence is found, last is returned. (since C++11)

[edit] Complexity

does at most S*(N-S+1) comparisons where S = distance(s_first, s_last) and N = distance(first, last).

[edit] Possible implementation

[edit] Example

The following code uses find_end() to search for two different sequences of numbers.

#include <algorithm>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v{1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4};
    std::vector<int>::iterator result;
 
    std::vector<int> t1{1, 2, 3};
 
    result = std::find_end(v.begin(), v.end(), t1.begin(), t1.end());
    if (result == v.end()) {
        std::cout << "subsequence not found\n";
    } else {
        std::cout << "last subsequence is at: "
                  << std::distance(v.begin(), result) << "\n";
    }
 
    std::vector<int> t2{4, 5, 6};
    result = std::find_end(v.begin(), v.end(), t2.begin(), t2.end());
    if (result == v.end()) {
        std::cout << "subsequence not found\n";
    } else {
        std::cout << "last subsequence is at: " 
                  << std::distance(v.begin(), result) << "\n";
    }
}

Output:

last subsequence is at: 8
subsequence not found

[edit] See also

finds two identical (or some other relationship) items adjacent to each other
(function template) [edit]
finds the first element satisfying specific criteria
(function template) [edit]
searches for any one of a set of elements
(function template) [edit]
searches for a number consecutive copies of an element in a range
(function template) [edit]