std::span

#include <algorithm>
#include <cstddef>
#include <iostream>
#include <span>
 
template<class T, std::size_t N>
[[nodiscard]]
constexpr auto slide(std::span<T, N> s, std::size_t offset, std::size_t width)
{
 return s.subspan(offset, offset + width <= s.size() ? width : 0U);
}
 
template<class T, std::size_t N, std::size_t M>
constexpr bool starts_with(std::span<T, N> data, std::span<T, M> prefix)
{
 return data.size() >= prefix.size()
 && std::equal (prefix.begin(), prefix.end(), data.begin());
}
 
template<class T, std::size_t N, std::size_t M>
constexpr bool ends_with(std::span<T, N> data, std::span<T, M> suffix)
{
 return data.size() >= suffix.size()
 && std::equal (data.end() - suffix.size(), data.end(),
 suffix.end() - suffix.size());
}
 
template<class T, std::size_t N, std::size_t M>
constexpr bool contains(std::span<T, N> span, std::span<T, M> sub)
{
 return std::ranges::search (span, sub).begin() != span.end();
}
 
void println(const auto& seq)
{
 for (const auto& elem : seq)
 std::cout << elem << ' ';
 std::cout << '\n';
}
 
int main()
{
 constexpr int a[]{0, 1, 2, 3, 4, 5, 6, 7, 8};
 constexpr int b[]{8, 7, 6};
 constexpr static std::size_t width{6};
 
 for (std::size_t offset{}; ; ++offset)
 if (auto s = slide(std::span{a}, offset, width); !s.empty())
 println(s);
 else
 break;
 
 static_assert(""
 && starts_with(std::span{a}, std::span{a, 4})
 && starts_with(std::span{a + 1, 4}, std::span{a + 1, 3})
 && !starts_with(std::span{a}, std::span{b})
 && !starts_with(std::span{a, 8}, std::span{a + 1, 3})
 && ends_with(std::span{a}, std::span{a + 6, 3})
 && !ends_with(std::span{a}, std::span{a + 6, 2})
 && contains(std::span{a}, std::span{a + 1, 4})
 && !contains(std::span{a, 8}, std::span{a, 9})
 );
}

0 1 2 3 4 5
1 2 3 4 5 6
2 3 4 5 6 7
3 4 5 6 7 8