std::search

 

C++

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Filesystem library (C++17)

Technical Specifications

 

Algorithm library

Execution policies (C++17)
is_execution_policy	execution::seqexecution::parexecution::par_unseq	execution::sequenced_policyexecution::parallel_policyexecution::parallel_unsequenced_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 adjacent_find	findfind_iffind_if_not (C++11) find_end find_first_of	search search_n lexicographical_compare lexicographical_compare_3way (C++20)
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_move (C++17)	uninitialized_copy_n (C++11) uninitialized_move_n (C++17)	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) compare_3way (C++20)
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>
	(1)
template< class ForwardIt1, class ForwardIt2 > ForwardIt1 search( ForwardIt1 first, ForwardIt1 last,                    ForwardIt2 s_first, ForwardIt2 s_last );			(until C++20)
template< class ForwardIt1, class ForwardIt2 > constexpr ForwardIt1 search( ForwardIt1 first, ForwardIt1 last,                              ForwardIt2 s_first, ForwardIt2 s_last );			(since C++20)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > ForwardIt1 search( ExecutionPolicy&& policy, ForwardIt1 first, ForwardIt1 last,                    ForwardIt2 s_first, ForwardIt2 s_last );		(2)	(since C++17)
		(3)
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > ForwardIt1 search( ForwardIt1 first, ForwardIt1 last,                    ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p );				(until C++20)
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > constexpr ForwardIt1 search( ForwardIt1 first, ForwardIt1 last,                              ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p );				(since C++20)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class BinaryPredicate > ForwardIt1 search( ExecutionPolicy&& policy, ForwardIt1 first, ForwardIt1 last,                    ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p );			(4)	(since C++17)
			(5)
template<class ForwardIterator, class Searcher> ForwardIterator search( ForwardIterator first, ForwardIterator last,                         const Searcher& searcher );					(since C++17) (until C++20)
template<class ForwardIterator, class Searcher> constexpr ForwardIterator search( ForwardIterator first, ForwardIterator last,                                   const Searcher& searcher );					(since C++20)

1-4) Searches for the first occurrence of the subsequence of elements [s_first, s_last) in the range [first, last - (s_last - s_first)).

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

5) Searches the sequence [first, last) for the pattern specified in the constructor of searcher. Effectively executes return searcher(first, last).first;. Searcher need not be CopyConstructible.

The standard library provides the following searchers: default_searcher (C++17) standard C++ library search algorithm implementation (class template) boyer_moore_searcher (C++17) Boyer-Moore search algorithm implementation (class template) boyer_moore_horspool_searcher (C++17) Boyer-Moore-Horspool search algorithm implementation (class template)

(since C++17)

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.
searcher	-	the searcher encapsulating the search algorithm and the pattern to look 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 ForwardIt1 and ForwardIt2 can be dereferenced and then implicitly converted to both Type1 and Type2. ​
Type requirements
- ForwardIt1, ForwardIt2 must meet the requirements of ForwardIterator.
- Searcher must meet the requirements of Searcher.

Return value

1-4) Iterator to the beginning of first subsequence [s_first, s_last) in the range [first, last - (s_last - s_first)). If no such subsequence is found, last is returned.
If [s_first, s_last) is empty, first is returned. (since C++11)

5) Returns the result of searcher.operator(), that is, an iterator to the location at which the substring is found or a copy of last if it was not found.

Complexity

1-4) At most S*N comparisons where S = std::distance(s_first, s_last) and N = std::distance(first, last).

5) Depends on the searcher

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 and ExecutionPolicy is one of the three standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

First version
template<class ForwardIt1, class ForwardIt2> ForwardIt1 search(ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last) { for (; ; ++first) { ForwardIt1 it = first; for (ForwardIt2 s_it = s_first; ; ++it, ++s_it) { if (s_it == s_last) { return first; } if (it == last) { return last; } if (!(*it == *s_it)) { break; } } } }
Second version
template<class ForwardIt1, class ForwardIt2, class BinaryPredicate> ForwardIt1 search(ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p) { for (; ; ++first) { ForwardIt1 it = first; for (ForwardIt2 s_it = s_first; ; ++it, ++s_it) { if (s_it == s_last) { return first; } if (it == last) { return last; } if (!p(*it, *s_it)) { break; } } } }

Example

Run this code

#include <string>
#include <algorithm>
#include <iostream>
#include <vector>
#include <functional>
 
template <typename Container>
bool in_quote(const Container& cont, const std::string& s)
{
    return std::search(cont.begin(), cont.end(), s.begin(), s.end()) != cont.end();
}
 
int main()
{
    std::string str = "why waste time learning, when ignorance is instantaneous?";
    // str.find() can be used as well
    std::cout << std::boolalpha << in_quote(str, "learning") << '\n'
                                << in_quote(str, "lemming")  << '\n';
 
    std::vector<char> vec(str.begin(), str.end());
    std::cout << std::boolalpha << in_quote(vec, "learning") << '\n'
                                << in_quote(vec, "lemming")  << '\n';
 
    // The C++17 overload demo:
    std::string in = "Lorem ipsum dolor sit amet, consectetur adipiscing elit,"
                     " sed do eiusmod tempor incididunt ut labore et dolore magna aliqua";
    std::string needle = "pisci";
    auto it = std::search(in.begin(), in.end(),
                   std::boyer_moore_searcher(
                      needle.begin(), needle.end()));
    if(it != in.end())
        std::cout << "The string " << needle << " found at offset "
                  << it - in.begin() << '\n';
    else
        std::cout << "The string " << needle << " not found\n";
}

Output:

true
false
true
false
The string pisci found at offset 43

See also

find_end	finds the last sequence of elements in a certain range (function template)
includes	returns true if one set is a subset of another (function template)
equal	determines if two sets of elements are the same (function template)
findfind_iffind_if_not (C++11)	finds the first element satisfying specific criteria (function template)
lexicographical_compare	returns true if one range is lexicographically less than another (function template)
mismatch	finds the first position where two ranges differ (function template)
search_n	searches for a number consecutive copies of an element in a range (function template)
default_searcher (C++17)	standard C++ library search algorithm implementation (class template)
boyer_moore_searcher (C++17)	Boyer-Moore search algorithm implementation (class template)
boyer_moore_horspool_searcher (C++17)	Boyer-Moore-Horspool search algorithm implementation (class template)