std::search

 

C++

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Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Algorithm library

Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
is_execution_policy (C++17)	execution::seqexecution::parexecution::par_unseqexecution::unseq (C++17)(C++17)(C++17)(C++20)	execution::sequenced_policyexecution::parallel_policyexecution::parallel_unsequenced_policyexecution::parallel_unsequenced (C++17)(C++17)(C++17)(C++20)
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	search search_n lexicographical_compare lexicographical_compare_three_way (C++20)	findfind_iffind_if_not (C++11) find_end find_first_of
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) shift_leftshift_right (C++20)(C++20) 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)
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)	transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)	partial_sum inclusive_scan (C++17) exclusive_scan (C++17)
Operations on uninitialized storage
uninitialized_copy uninitialized_move (C++17) uninitialized_fill	uninitialized_copy_n (C++11) uninitialized_move_n (C++17) uninitialized_fill_n	uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17)	destroy (C++17) destroy_n (C++17) destroy_at (C++17) construct_at (C++20)
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 ForwardIt, class Searcher > ForwardIt search( ForwardIt first, ForwardIt last,                   const Searcher& searcher );					(since C++17) (until C++20)
template< class ForwardIt, class Searcher > constexpr ForwardIt search( ForwardIt first, ForwardIt last,                             const Searcher& searcher );					(since C++20)

1-4) Searches for the first occurrence of the sequence 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.	(until C++20)
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true.	(since C++20)

5) Searches the range [first, last) for the pattern specified in the constructor of searcher. 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); 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. ​
Type requirements
- ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardIterator.

Return value

1-4) Iterator to the beginning of first occurrence of the sequence [s_first, s_last) in the range [first, last). If no such occurrence is found, last is returned.

If [s_first, s_last) is empty, first is returned.

5) searcher(first, last).first.

Complexity

1-4) Given \(\scriptsize N\)N as std::distance(first, last) and \(\scriptsize S\)S as std::distance(s_first, s_last):

1,2) At most \(\scriptsize N\cdot S\)N·S comparisons using operator==.

3,4) At most \(\scriptsize N\cdot S\)N·S applications of the predicate p.

5) Depends on 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 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

search (1)
template<class ForwardIt1, class ForwardIt2> constexpr ForwardIt1 search(ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last) { while (true) { 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; } ++first; } }
search (3)
template<class ForwardIt1, class ForwardIt2, class BinaryPredicate> constexpr ForwardIt1 search(ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p) { while (true) { 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; } ++first; } }

Example

Run this code

#include <algorithm>
#include <cassert>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <string_view>
#include <vector>
 
using namespace std::literals;
 
bool contains(const auto& cont, std::string_view s)
{
    // str.find() (or str.contains(), since C++23) can be used as well
    return std::search(cont.begin(), cont.end(), s.begin(), s.end()) != cont.end();
}
 
int main()
{
    const auto str{"why waste time learning, when ignorance is instantaneous?"sv};
    assert(contains(str, "learning"));
    assert(not contains(str, "lemming"));
 
    const std::vector vec(str.begin(), str.end());
    assert(contains(vec, "learning"));
    assert(not contains(vec, "leaning"));
 
    // The C++17 overload with searchers demo:
    constexpr auto quote
    {
        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed "
        "do eiusmod tempor incididunt ut labore et dolore magna aliqua"sv
    };
 
    for (const auto word : {"pisci"sv, "Pisci"sv})
    {
        std::cout << "The string " << std::quoted(word) << ' ';
        const std::boyer_moore_searcher searcher(word.begin(), word.end());
        const auto it = std::search(quote.begin(), quote.end(), searcher);
        if (it == quote.end())
            std::cout << "not found\n";
        else
            std::cout << "found at offset " << std::distance(quote.begin(), it) << '\n';
    }
}

Output:

The string "pisci" found at offset 43
The string "Pisci" 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
LWG 1205	C++98	the return value was unclear if [s_first, s_last) is empty	returns first in this case
LWG 1338	C++98	the resolution of LWG issue 1205 was incorrectly applied, making first to be returned if no occurence is found	returns last in this case

See also

find_end	finds the last sequence of elements in a certain range (function template)
includes	returns true if one sequence is a subsequence 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 a range for a number of consecutive copies of an element (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)
ranges::search (C++20)	searches for a range of elements (niebloid)