std::search

 

C++

Compiler support

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)

Execution support library (C++26)

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 Batch operations for_each for_each_n (C++17) Search operations all_ofany_ofnone_of (C++11)                (C++11)(C++11) countcount_if mismatch equal findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n Modifying sequence operations Copy operations copycopy_if (C++11) copy_backward copy_n (C++11) move (C++11) move_backward (C++11) Swap operations swap iter_swap swap_ranges Transformation operations replacereplace_if transform replace_copyreplace_copy_if Generation operations fill fill_n generate generate_n Removing operations removeremove_if unique remove_copyremove_copy_if unique_copy Order-changing operations reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) shift_leftshift_right (C++20)(C++20) Sampling operations sample (C++17)	Sorting and related operations Partitioning operations partition partition_copy (C++11)   stable_partition is_partitioned (C++11) partition_point (C++11) Sorting operations sort stable_sort partial_sort partial_sort_copy is_sorted (C++11) is_sorted_until (C++11) nth_element Binary search operations (on partitioned ranges) lower_bound upper_bound equal_range binary_search Set operations (on sorted ranges) includes set_union set_intersection set_difference set_symmetric_difference Merge operations (on sorted ranges) merge inplace_merge Heap operations push_heap pop_heap make_heap sort_heap is_heap (C++11) is_heap_until (C++11) Minimum/maximum operations max min minmax (C++11) clamp (C++17) max_element min_element minmax_element (C++11) Lexicographical comparison operations lexicographical_compare lexicographical_compare_three_way (C++20) Permutation operations next_permutation prev_permutation is_permutation (C++11) C library qsort bsearch
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)
Operations on uninitialized memory
uninitialized_copy uninitialized_move (C++17)    uninitialized_fill uninitialized_copy_n (C++11) uninitialized_move_n (C++17) uninitialized_fill_n	destroy (C++17) destroy_n (C++17) destroy_at (C++17) construct_at (C++20)       uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17)

 

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 participate in overload resolution only if

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 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); 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.
- Searcher must meet the requirements of Searcher.

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.(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 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 <functional>
#include <iomanip>
#include <iostream>
#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};
 
    std::cout << std::boolalpha
              << contains(str, "learning") << '\n'   // true
              << contains(str, "lemming")  << '\n';  // false
 
    const std::vector vec(str.begin(), str.end());
    std::cout << contains(vec, "learning") << '\n'   // true
              << contains(vec, "leaning")  << '\n';  // false
 
    // The C++17 overload with searchers demo:
    constexpr auto haystack
    {
        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed "
        "do eiusmod tempor incididunt ut labore et dolore magna aliqua"sv
    };
 
    for (const auto needle : {"pisci"sv, "Pisci"sv})
    {
        const std::boyer_moore_searcher searcher(needle.begin(), needle.end());
        const auto it = std::search(haystack.begin(), haystack.end(), searcher);
        std::cout << "The string " << std::quoted(needle) << ' ';
        if (it == haystack.end())
            std::cout << "not found\n";
        else
            std::cout << "found at offset " << it - haystack.begin() << '\n';
    }
}

Output:

true
false
true
false
The string "pisci" found at offset 43
The string "Pisci" not found

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 for the first occurrence of 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)
ranges::search (C++20)	searches for the first occurrence of a range of elements (niebloid)