std::ranges::upper_bound - cppreference.com (original) (raw)

| Defined in header | | | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | --------------------------- | | Call signature | | | | (1) | | | | template< std::forward_iterator I, std::sentinel_for<I> S, class T, class Proj = std::identity, std::indirect_strict_weak_order <const T*, std::projected<I, Proj>> Comp = ranges::less > constexpr I upper_bound( I first, S last, const T& value, Comp comp = {}, Proj proj = {} ); | | (since C++20) (until C++26) | | template< std::forward_iterator I, std::sentinel_for<I> S, class Proj = std::identity, class T = std::projected_value_t<I, Proj>, std::indirect_strict_weak_order <const T*, std::projected<I, Proj>> Comp = ranges::less > constexpr I upper_bound( I first, S last, const T& value, Comp comp = {}, Proj proj = {} ); | | (since C++26) | | (2) | | | | template< ranges::forward_range R, class T, class Proj = std::identity, std::indirect_strict_weak_order <const T*, std::projected<ranges::iterator_t<R>, Proj>> Comp = ranges::less > constexpr ranges::borrowed_iterator_t<R> upper_bound( R&& r, const T& value, Comp comp = {}, Proj proj = {} ); | | (since C++20) (until C++26) | | template< ranges::forward_range R, class Proj = std::identity, class T = std::projected_value_t<ranges::iterator_t<R>, Proj>, std::indirect_strict_weak_order <const T*, std::projected<ranges::iterator_t<R>, Proj>> Comp = ranges::less > constexpr ranges::borrowed_iterator_t<R> upper_bound( R&& r, const T& value, Comp comp = {}, Proj proj = {} ); | | (since C++26) |

1. Returns an iterator pointing to the first element in the range [first, last) that is greater than value, or last if no such element is found. The range [first, last) must be partitioned with respect to the expression or !comp(value, element), i.e., all elements for which the expression is true must precede all elements for which the expression is false. A fully-sorted range meets this criterion.

2. Same as (1), but uses r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last.

The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:

• Explicit template argument lists cannot be specified when calling any of them.
• None of them are visible to argument-dependent lookup.
• When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Possible implementation
• 5 Notes
• 6 Example
• 7 See also

[edit] Parameters

[edit] Return value

Iterator pointing to the first element that is greater than value, or last if no such element is found.

[edit] Complexity

The number of comparisons and applications of the projection performed are logarithmic in the distance between first and last (at most log2(last - first) + O(1) comparisons and applications of the projection). However, for an iterator that does not model random_access_iterator, the number of iterator increments is linear.

[edit] Possible implementation

struct upper_bound_fn { template<std::forward_iterator I, std::sentinel_for S, class Proj = std::identity, class T = std::projected_value_t<I, Proj>, std::indirect_strict_weak_order <const T*, std::projected<I, Proj>> Comp = ranges::less> constexpr I operator()(I first, S last, const T& value, Comp comp = {}, Proj proj = {}) const { I it; std::iter_difference_t count, step; count = ranges::distance(first, last);   while (count > 0) { it = first; step = count / 2; ranges::advance(it, step, last); if (!comp(value, std::invoke(proj, *it))) { first = ++it; count -= step + 1; } else count = step; } return first; }   template<ranges::forward_range R, class Proj = std::identity, class T = std::projected_value_t<ranges::iterator_t, Proj>, std::indirect_strict_weak_order <const T*, std::projected<ranges::iterator_t, Proj>> Comp = ranges::less> constexpr ranges::borrowed_iterator_t operator()(R&& r, const T& value, Comp comp = {}, Proj proj = {}) const { return (*this)(ranges::begin(r), ranges::end(r), value, std::ref(comp), std::ref(proj)); } };   inline constexpr upper_bound_fn upper_bound;

[edit] Notes

[edit] Example

#include #include #include #include #include #include   int main() { namespace ranges = std::ranges;   std::vector data{1, 1, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 6};   { auto lower = ranges::lower_bound(data.begin(), data.end(), 4); auto upper = ranges::upper_bound(data.begin(), data.end(), 4);   ranges::copy(lower, upper, std::ostream_iterator(std::cout, " ")); std::cout << '\n'; } { auto lower = ranges::lower_bound(data, 3); auto upper = ranges::upper_bound(data, 3);   ranges::copy(lower, upper, std::ostream_iterator(std::cout, " ")); std::cout << '\n'; }   using CD = std::complex; std::vector nums{{1, 0}, {2, 2}, {2, 1}, {3, 0}, {3, 1}}; auto cmpz = [](CD x, CD y) { return x.real() < y.real(); }; #ifdef __cpp_lib_algorithm_default_value_type auto it = ranges::upper_bound(nums, {2, 0}, cmpz); #else auto it = ranges::upper_bound(nums, CD{2, 0}, cmpz); #endif assert((*it == CD{3, 0})); }

Output:

[edit] See also

| | returns range of elements matching a specific key(algorithm function object)[edit] | | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | returns an iterator to the first element not less than the given value(algorithm function object)[edit] | | | divides a range of elements into two groups(algorithm function object)[edit] | | | returns an iterator to the first element greater than a certain value (function template) [edit] |