std::ranges::upper_bound
Defined in header <algorithm>
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Call signature |
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template< std::forward_iterator I, std::sentinel_for<I> S, class T, class Proj = std::identity, |
(1) | (since C++20) |
template< ranges::forward_range R, class T, class Proj = std::identity, std::indirect_strict_weak_order< |
(2) | (since C++20) |
[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.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 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.
In practice, they may be implemented as function objects, or with special compiler extensions.
Contents |
Parameters
first, last | - | iterator-sentinel defining the partially-ordered range to examine |
r | - | the partially-ordered range to examine |
value | - | value to compare the elements to |
pred | - | predicate to apply to the projected elements |
proj | - | projection to apply to the elements |
Return value
Iterator pointing to the first element that is greater than value
, or last
if no such element is found.
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.
Possible implementation
struct upper_bound_fn { 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 operator()( I first, S last, const T& value, Comp comp = {}, Proj proj = {} ) const { I it; std::iter_difference_t<I> 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 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> 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; |
Example
#include <algorithm> #include <iostream> #include <iterator> #include <vector> int main() { namespace ranges = std::ranges; std::vector<int> 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<int>(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<int>(std::cout, " ")); std::cout << '\n'; } }
Output:
4 4 4 3 3 3 3
See also
(C++20) |
returns range of elements matching a specific key (niebloid) |
(C++20) |
returns an iterator to the first element not less than the given value (niebloid) |
(C++20) |
divides a range of elements into two groups (niebloid) |
returns an iterator to the first element greater than a certain value (function template) |