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

Returns true if the sorted range [first2, last2) is a subsequence of the sorted range [first1, last1) (a subsequence need not be contiguous).

1. If [first1, last1) or [first2, last2) is not sorted with respect to operator<(until C++20)std::less{}(since C++20), the behavior is undefined.

2. If [first1, last1) or [first2, last2) is not sorted with respect to comp, the behavior is undefined.

2,4) Same as (1,3), but executed according to policy.

These overloads participate in overload resolution only if all following conditions are satisfied:

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

true if [first2, last2) is a subsequence of [first1, last1); otherwise false.

An empty sequence is a subsequence of any sequence, so true is returned if [first2, last2) is empty.

[edit] Complexity

Given \(\scriptsize N_1\)N1 as std::distance(first1, last1) and \(\scriptsize N_2\)N2 as std::distance(first2, last2):

1,2) At most \(\scriptsize 2 \cdot (N_1+N_2)-1\)2⋅(N1+N2)-1 comparisons using operator<(until C++20)std::less{}(since C++20).

3,4) At most \(\scriptsize 2 \cdot (N_1+N_2)-1\)2⋅(N1+N2)-1 applications of the comparison function comp.

[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   template<class Os, class Co> Os& operator<<(Os& os, const Co& v) { for (const auto& i : v) os << i << ' '; return os << '\t'; }   int main() { const auto v1 = {'a', 'b', 'c', 'f', 'h', 'x'}, v2 = {'a', 'b', 'c'}, v3 = {'a', 'c'}, v4 = {'a', 'a', 'b'}, v5 = {'g'}, v6 = {'a', 'c', 'g'}, v7 = {'A', 'B', 'C'};   auto no_case = [](char a, char b) { return std::tolower(a) < std::tolower(b); };   std::cout << v1 << "\nincludes:\n" << std::boolalpha << v2 << ": " << std::includes(v1.begin(), v1.end(), v2.begin(), v2.end()) << '\n' << v3 << ": " << std::includes(v1.begin(), v1.end(), v3.begin(), v3.end()) << '\n' << v4 << ": " << std::includes(v1.begin(), v1.end(), v4.begin(), v4.end()) << '\n' << v5 << ": " << std::includes(v1.begin(), v1.end(), v5.begin(), v5.end()) << '\n' << v6 << ": " << std::includes(v1.begin(), v1.end(), v6.begin(), v6.end()) << '\n' << v7 << ": " << std::includes(v1.begin(), v1.end(), v7.begin(), v7.end(), no_case) << " (case-insensitive)\n"; }

Output:

a b c f h x includes: a b c  : true a c  : true a a b  : false g  : false a c g  : false A B C  : true (case-insensitive)

[edit] Defect reports

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

[edit] See also

| | computes the difference between two sets (function template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | searches for the first occurrence of a range of elements (function template) [edit] | | | returns true if one sequence is a subsequence of another(algorithm function object)[edit] |