ForwardIt1 find_end( ForwardIt1 first, ForwardIt1 last,
ForwardIt1 find_end( ExecutionPolicy&& policy,
ForwardIt1 first, ForwardIt1 last,
ForwardIt1 find_end( ForwardIt1 first, ForwardIt1 last,
ForwardIt2 s_first, ForwardIt2 s_last,
class ForwardIt1, class ForwardIt2, class BinaryPred >
ForwardIt1 find_end( ExecutionPolicy&& policy,
ForwardIt1 first, ForwardIt1 last,
ForwardIt2 s_first, ForwardIt2 s_last,
Searches for the last occurrence of the sequence [
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 participate in overload resolution only if all following conditions are satisfied:
[edit] Parameters first, last - the pair of iterators defining the range of elements to examine s_first, s_last - the pair of iterators defining the range of elements to search for policy - the execution policy to use p - binary predicate which returns âtrue 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);
While the signature does not need to have const &, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1
and Type2
regardless of value category (thus, Type1 & is not allowed, nor is Type1 unless for Type1
a move is equivalent to a copy(since C++11)).
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. â
ForwardIt1
must meet the requirements of LegacyForwardIterator. -ForwardIt2
must meet the requirements of LegacyForwardIterator. [edit] Return value
Iterator to the beginning of last occurrence of the sequence [
s_first,
s_last)
in range [
first,
last)
.
If [
s_first,
s_last)
is empty or if no such sequence is found, last is returned.
Given \(\scriptsize N\)N as std::distance(first, last) and \(\scriptsize S\)S as std::distance(s_first, s_last):
1,2) At most \(\scriptsize S\cdot(N-S+1)\)S·(N-S+1) comparisons using operator==.
3,4) At most \(\scriptsize S\cdot(N-S+1)\)S·(N-S+1) applications of the predicate p.
[edit] ExceptionsThe overloads with a template parameter named ExecutionPolicy
report errors as follows:
ExecutionPolicy
is one of the standard policies, std::terminate is called. For any other ExecutionPolicy
, the behavior is implementation-defined.template<class ForwardIt1, class ForwardIt2> constexpr //< since C++20 ForwardIt1 find_end(ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last) { if (s_first == s_last) return last; ForwardIt1 result = last; while (true) { ForwardIt1 new_result = std::search(first, last, s_first, s_last); if (new_result == last) break; else { result = new_result; first = result; ++first; } } return result; }find_end (3)
template<class ForwardIt1, class ForwardIt2, class BinaryPred> constexpr //< since C++20 ForwardIt1 find_end(ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last, BinaryPred p) { if (s_first == s_last) return last; ForwardIt1 result = last; while (true) { ForwardIt1 new_result = std::search(first, last, s_first, s_last, p); if (new_result == last) break; else { result = new_result; first = result; ++first; } } return result; }[edit] Example
#include <algorithm> #include <array> #include <cmath> #include <iostream> auto print_result = [](auto result, const auto& v) { result == v.end() ? std::cout << "Sequence not found\n" : std::cout << "Last occurrence is at: " << std::distance(v.begin(), result) << '\n'; }; int main() { const auto v = {1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4}; for (auto const& x : {std::array{1, 2, 3}, {4, 5, 6}}) { auto iter = std::find_end(v.begin(), v.end(), x.begin(), x.end()); // overload (1) print_result(iter, v); } for (auto const& x : {std::array{-1, -2, -3}, {-4, -5, -6}}) { auto iter = std::find_end(v.begin(), v.end(), x.begin(), x.end(), // overload (3) [](int x, int y) { return std::abs(x) == std::abs(y); }); print_result(iter, v); } }
Output:
Last occurrence is at: 8 Sequence not found Last occurrence is at: 8 Sequence not found[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 1205 C++98 the return value was unclear if[
s_first,
s_last)
is empty returns last in this case LWG 2150 C++98 the condition of âsequence occurenceâ was incorrect corrected [edit] See also searches for the first occurrence of a range of elements
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