std::search - cppreference.com (original) (raw)

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==.

2. 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:

1. Searches the range [first, last) for the pattern specified in the constructor of searcher.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Exceptions
• 5 Possible implementation
• 6 Example
• 7 Defect reports
• 8 See also

[edit] Parameters

[edit] 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.

1. searcher(first, last).first.

[edit] 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.

1. Depends on searcher.

[edit] 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.

[edit] Possible implementation

[edit] Example

#include #include #include #include #include #include #include #include   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

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also