std::find_end

 

C++

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Regular expressions library (C++11)

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Filesystem library (C++17)

Technical Specifications

 

Algorithm library

Execution policies (C++17)
is_execution_policy	sequentialparpar_vec	sequential_execution_policyparallel_execution_policyparallel_vector_execution_policy
Non-modifying sequence operations
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each for_each_n (C++17)	countcount_if mismatch equal lexicographical_compare	findfind_iffind_if_not (C++11) find_end find_first_of	adjacent_find search search_n
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) transform	fill fill_n generate generate_n swap iter_swap swap_ranges sample (C++17)	removeremove_if replacereplace_if reverse rotate unique random_shuffle (until C++17)	remove_copyremove_copy_if replace_copyreplace_copy_if reverse_copy rotate_copy unique_copy shuffle (C++11)
Operations on uninitialized storage
uninitialized_copy	uninitialized_copy_n	uninitialized_fill	uninitialized_fill_n
Partitioning operations
is_partitioned (C++11) partition_point (C++11)	partition partition_copy (C++11)	stable_partition
Sorting operations
is_sorted (C++11) is_sorted_until (C++11)	sort stable_sort	partial_sort partial_sort_copy	nth_element
Binary search operations
lower_bound	upper_bound	binary_search	equal_range
Set operations (on sorted ranges)
merge inplace_merge	set_difference set_intersection	set_symmetric_difference set_union	includes
Heap operations
is_heap (C++11) is_heap_until (C++11)	make_heap sort_heap	push_heap pop_heap
Minimum/maximum operations
max max_element	min min_element	minmax (C++11) minmax_element (C++11)	clamp (C++17)
Permutations
is_permutation (C++11)	next_permutation	prev_permutation
Numeric operations
iota (C++11) inner_product adjacent_difference	accumulate reduce (C++17) transform_reduce (C++17)	partial_sum inclusive_scan (C++17) exclusive_scan (C++17)	transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)
C library
qsort	bsearch

 

Defined in header <algorithm>
template< class ForwardIt1, class ForwardIt2 > ForwardIt1 find_end( ForwardIt1 first, ForwardIt1 last,                      ForwardIt2 s_first, ForwardIt2 s_last );	(1)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > ForwardIt1 find_end( ExecutionPolicy&& policy, ForwardIt1 first, ForwardIt1 last,                      ForwardIt2 s_first, ForwardIt2 s_last );	(2)	(since C++17)
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > ForwardIt1 find_end( ForwardIt1 first, ForwardIt1 last,                      ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p );	(3)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class BinaryPredicate > ForwardIt1 find_end( ExecutionPolicy&& policy, ForwardIt1 first, ForwardIt1 last,                      ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p );	(4)	(since C++17)

Searches for the last subsequence of elements [s_first, s_last) in the range [first, last).

1) Elements are compared using operator==.

3) Elements are compared using the given binary predicate p.

2,4) Same as (1,3), but executed according to policy. These overloads do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Parameters

first, last	-	the range of elements to examine
s_first, s_last	-	the range of elements to search for
policy	-	the execution policy to use. See execution policy for details.
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 ForwardIt1 and ForwardIt2 can be dereferenced and then implicitly converted to Type1 and Type2 respectively. ​
Type requirements
- ForwardIt1 must meet the requirements of ForwardIterator.
- ForwardIt2 must meet the requirements of ForwardIterator.

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)

Complexity

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

Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception,

• if policy is std::parallel_vector_execution_policy, std::terminate is called
• if policy is std::sequential_execution_policy or std::parallel_execution_policy, the algorithm exits with an std::exception_list containing all uncaught exceptions. If there was only one uncaught exception, the algorithm may rethrow it without wrapping in std::exception_list. It is unspecified how much work the algorithm will perform before returning after the first exception was encountered.
• if policy is some other type, the behavior is implementation-defined

• If the algorithm fails to allocate memory (either for itself or to construct an std::exception_list when handling a user exception), std::bad_alloc is thrown.

Possible implementation

First version
template<class ForwardIt1, class ForwardIt2> ForwardIt1 find_end(ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last) { if (s_first == s_last) return last; ForwardIt1 result = last; while (1) { ForwardIt1 new_result = std::search(first, last, s_first, s_last); if (new_result == last) { return result; } else { result = new_result; first = result; ++first; } } return result; }
Second version
template<class ForwardIt1, class ForwardIt2, class BinaryPredicate> ForwardIt1 find_end(ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p) { if (s_first == s_last) return last; ForwardIt1 result = last; while (1) { ForwardIt1 new_result = std::search(first, last, s_first, s_last, p); if (new_result == last) { return result; } else { result = new_result; first = result; ++first; } } return result; }

Example

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

Run this code

#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

See also

search	searches for a range of elements (function template)
includes	returns true if one set is a subset of another (function template)
adjacent_find	finds the first two adjacent items that are equal (or satisfy a given predicate) (function template)
findfind_iffind_if_not (C++11)	finds the first element satisfying specific criteria (function template)
find_first_of	searches for any one of a set of elements (function template)
search_n	searches for a number consecutive copies of an element in a range (function template)
std::experimental::parallel::find_end (parallelism TS)	parallelized version of std::find_end (function template)