std::ranges::includes() 算法

自 C++20 起

简化

// (1)
constexpr bool
    includes( I1 first1, S1 last1, I2 first2, S2 last2,
              Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )

// (2)
constexpr bool
    includes( R1&& r1, R2&& r2, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )

参数类型是泛型的，并具有以下约束

• I1, I2 - std::input_iterator

• S1, S2 - std::sentinel_for<I1>, std::sentinel_for<I2>

• R1, R2 - std::ranges::input_range

• O - std::weakly_incrementable

• Comp:

  • (1) - indirect_strict_weak_order<projected<I1, Proj1>, projected<I2, Proj2>>
  • (2) - indirect_strict_weak_order<projected<ranges::iterator_t<R1> Proj1>, projected<ranges::iterator_t<R2> Proj2>>

  (为便于阅读，此处省略了 std:: 命名空间)

• Proj1, Proj2 - (无)

所有重载的 Proj 和 Comp 模板参数具有以下默认类型：std::identity, ranges::less。

(为便于阅读，此处省略了 std:: 命名空间)

详细

// (1)
template<
  std::input_iterator I1,
  std::sentinel_for<I1> S1,
  std::input_iterator I2,
  std::sentinel_for<I2> S2,
  class Proj1 = std::identity,
  class Proj2 = std::identity,
  std::indirect_strict_weak_order<std::projected<I1, Proj1>,
                                  std::projected<I2, Proj2>> Comp = ranges::less
>
constexpr bool
    includes( I1 first1, S1 last1, I2 first2, S2 last2,
              Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )

// (2)
template<
  ranges::input_range R1
  ranges::input_range R2,
  class Proj1 = std::identity
  class Proj2 = std::identity,
  std::indirect_strict_weak_order<std::projected<ranges::iterator_t<R1> Proj1>,
                                  std::projected<ranges::iterator_t<R2> Proj2>> Comp = ranges::less
>
constexpr bool
    includes( R1&& r1, R2&& r2, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )

• (1) 如果排序范围 [first2; last2) 的投影是排序范围 [first1; last1) 的子序列，则返回 true。

  范围必须使用给定的比较函数 comp 进行排序。

  子序列不必是连续的。

• (2) 与 (1) 相同，但使用 r1 作为第一个范围，r2 作为第二个范围，如同使用 ranges::begin(r1) 作为 first1，ranges::end(r1) 作为 last1，ranges::begin(r2) 作为 first2，ranges::end(r2) 作为 last2。

本页描述的函数类实体是niebloids。

参数

first1 last1	要检查的已排序元素范围。
r r1	要检查的已排序元素范围。
first2 last2	要搜索的已排序元素范围。
r2	要搜索的已排序元素范围。
comp	应用于投影元素的比较函数。
proj1	应用于第一个范围中元素的投影。
proj2	应用于第二个范围中元素的投影。

返回值

如果 [first2; last2) 是 [first1; last1) 的子序列，则为 true。
否则为 false。

复杂度

给定 N1 为 ranges::distance(r1)，N2 为 ranges::distance(r2)

最多 2 * (N1 + N2 − 1) 次比较

异常

(无)

可能的实现

includes(1) 和 includes(2)

struct includes_fn
{
    template<std::input_iterator I1, std::sentinel_for<I1> S1,
             std::input_iterator I2, std::sentinel_for<I2> S2,
             class Proj1 = std::identity, class Proj2 = std::identity,
             std::indirect_strict_weak_order<
                 std::projected<I1, Proj1>,
                 std::projected<I2, Proj2>> Comp = ranges::less>
    constexpr bool operator()(I1 first1, S1 last1, I2 first2, S2 last2,
                              Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) const
    {
        for (; first2 != last2; ++first1)
        {
            if (first1 == last1 || comp(*first2, *first1))
                return false;
            if (!comp(*first1, *first2))
                ++first2;
        }
        return true;
    }

    template<ranges::input_range R1, ranges::input_range R2,
             class Proj1 = std::identity, class Proj2 = std::identity,
             std::indirect_strict_weak_order<
                 std::projected<ranges::iterator_t<R1>, Proj1>,
                 std::projected<ranges::iterator_t<R2>, Proj2>> Comp = ranges::less>
    constexpr bool operator()(R1&& r1, R2&& r2, Comp comp = {},
                              Proj1 proj1 = {}, Proj2 proj2 = {}) const
    {
        return (*this)(ranges::begin(r1), ranges::end(r1),
                       ranges::begin(r2), ranges::end(r2),
                       std::ref(comp), std::ref(proj1), std::ref(proj2));
    }
};

inline constexpr auto includes = includes_fn {};

示例

Main.cpp

#include <algorithm>
#include <cctype>
#include <initializer_list>
#include <iomanip>
#include <iostream>
#include <locale>
#include <string>

template<class T>
std::ostream& operator<<(std::ostream& os, std::initializer_list<T> const& list)
{
    for (os << "{ "; auto const& elem : list)
        os << elem << ' ';
    return os << "} ";
}

struct true_false : std::numpunct<char>
{
    std::string do_truename() const { return "? Yes\n"; }
    std::string do_falsename() const { return "? No\n"; }
};

int main()
{
    std::cout.imbue(std::locale(std::cout.getloc(), new true_false));

    auto ignore_case = [](char a, char b) { return std::tolower(a) < std::tolower(b); };

    const auto
        a = {'a', 'b', 'c'},
        b = {'a', 'c'},
        c = {'a', 'a', 'b'},
        d = {'g'},
        e = {'a', 'c', 'g'},
        f = {'A', 'B', 'C'},
        z = {'a', 'b', 'c', 'f', 'h', 'x'};

    std::cout
        << z << "includes\n" << std::boolalpha
        << a << std::ranges::includes(z.begin(), z.end(), a.begin(), a.end())
        << b << std::ranges::includes(z, b)
        << c << std::ranges::includes(z, c)
        << d << std::ranges::includes(z, d)
        << e << std::ranges::includes(z, e)
        << f << std::ranges::includes(z, f, ignore_case);
}

输出

{ a b c f h x } includes
{ a b c } ? Yes
{ a c } ? Yes
{ a a b } ? No
{ g } ? No
{ a c g } ? No
{ A B C } ? Yes