From cppreference.com
Defined in header
template<classForwardIt1,classForwardIt2>ForwardIt1find_end(ForwardIt1first1,ForwardIt1last1,ForwardIt2first2,ForwardIt2last2); (1)(constexpr since C++20)template<classForwardIt1,classForwardIt2,classBinaryPred>ForwardIt1find_end(ForwardIt1first1,ForwardIt1last1,ForwardIt2first2,ForwardIt2last2,BinaryPredp); (2)(constexpr since C++20)template<classExecutionPolicy,classForwardIt1,classForwardIt2>ForwardIt1find_end(ExecutionPolicy&&policy,ForwardIt1first1,ForwardIt1last1,ForwardIt2first2,ForwardIt2last2); (3) (since C++17)template<classExecutionPolicy,classForwardIt1,classForwardIt2,classBinaryPred>ForwardIt1find_end(ExecutionPolicy&&policy,ForwardIt1first1,ForwardIt1last1,ForwardIt2first2,ForwardIt2last2,BinaryPredp); (4) (since C++17)Searches for the last occurrence of the target range [first2, last2) in the source range [first1, last1).
1) Elements are compared using operator==.
2) Elements are compared using the given binary predicate p.
3,4) Same as (1,2), but executed according to policy.
These overloads participate in overload resolution only if the value of the following expression is true:
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>
(until C++20)std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
(since C++20)Parameters
first1, last1 - the pair of iterators defining the source
first2, last2 - the pair of iterators defining the target
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:
boolpred(constType1&a,constType2&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
(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.
policy - the
to use Type requirements -ForwardIt1 must meet the requirements of
. -ForwardIt2 must meet the requirements of
. Return value
Iterator to the beginning of the last occurrence of the target range in source range.
If the target range is empty or it does not appear in the source range, last1 is returned.
Complexity
Given N1 as std::distance(first1,last1) and N2 as std::distance(first2,last2):
1) At most N2⋅(N1-N2+1) comparisons using operator==.
2) At most N2⋅(N1-N2+1) applications of p.
3)𝓞(N2⋅(N1-N2+1)) comparisons using operator==.
4)𝓞(N2⋅(N1-N2+1)) applications of p.
Exceptions
3,4) During the execution process:
If the temporary memory resources required for parallelization are not available,
is thrown.
If an uncaught exception is thrown while accessing objects via an algorithm argument, the behavior is determined by the execution policy (for
,
is invoked).
Possible implementation
template<classForwardIt1,classForwardIt2>constexpr//< since C++20ForwardIt1find_end(ForwardIt1first1,ForwardIt1last1,ForwardIt2first2,ForwardIt2last2){if(first2==last2)returnlast1;ForwardIt1result=last1;while(true){ForwardIt1new_result=std::search(first1,last1,first2,last2);if(new_result==last1)break;else{result=new_result;first1=result;++first1;}}returnresult;}
template<classForwardIt1,classForwardIt2,classBinaryPred>constexpr//< since C++20ForwardIt1find_end(ForwardIt1first1,ForwardIt1last1,ForwardIt2first2,ForwardIt2last2,BinaryPredp){if(first2==last2)returnlast1;ForwardIt1result=last1;while(true){ForwardIt1new_result=std::search(first1,last1,first2,first2,p);if(new_result==last1)break;else{result=new_result;first1=result;++first1;}}returnresult;}Example
Run this code
#include<algorithm>#include<array>#include<cmath>#include<iostream>autoprint_result=[](autoresult,constauto&v){result==v.end()?std::cout<<"Sequence not found\n":std::cout<<"Last occurrence is at: "<<std::distance(v.begin(),result)<<'\n';};intmain(){constautov={1,2,3,4,1,2,3,4,1,2,3,4};for(constauto&x:{std::array{1,2,3},{4,5,6}}){autoiter=std::find_end(v.begin(),v.end(),x.begin(),x.end());// overload (1)print_result(iter,v);}for(constauto&x:{std::array{-1,-2,-3},{-4,-5,-6}}){autoiter=std::find_end(v.begin(),v.end(),x.begin(),x.end(),// overload (3)[](intx,inty){returnstd::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 Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
C++98 the return value was unclear if the target range is empty returns last1 in this case
C++98 the condition of “occurence” was incorrect corrected See also
(C++20)
finds the last sequence of elements in a certain range
(algorithm function object)
searches for the first occurrence of a range of elements
(function template & algorithm function object)
(C++20)
determines if one sequence is a subsequence of another
(function template & algorithm function object)
(C++20)
finds the first two adjacent items that are equal (or satisfy a given predicate)
(function template & algorithm function object)
(C++20)
(C++11)
finds the first element satisfying specific criteria
(function template & algorithm function object)
ranges::findranges::find_ifranges::find_if_not
(C++20)(C++20)(C++20)
searches for any one of a set of elements
(function template & algorithm function object)
(C++20)
searches for the first occurrence of a number consecutive copies of an element in a range
(function template & algorithm function object)
(C++20)