Namespaces
Variants
Views
Actions

std::ranges::upper_bound

From cppreference.com
< cpp‎ | algorithm‎ | ranges
 
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
Batch operations
(C++17)
Search operations
(C++11)                (C++11)(C++11)

Modifying sequence operations
Copy operations
(C++11)
(C++11)
Swap operations
Transformation operations
Generation operations
Removing operations
Order-changing operations
(until C++17)(C++11)
(C++20)(C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
Heap operations
Minimum/maximum operations
(C++11)
(C++17)
Lexicographical comparison operations
Permutation operations
C library
Numeric operations
Operations on uninitialized memory
 
Constrained algorithms
Non-modifying sequence operations
Modifying sequence operations
Partitioning operations
Sorting operations
Binary search operations (on sorted ranges)
ranges::upper_bound
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
Permutation operations
Numeric operations
Fold operations
Operations on uninitialized storage
Random number generation
Return types
 
Defined in header <algorithm>
Call signature
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 = {} );
(1) (since C++20)
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 = {} );
(2) (since C++20)
1) Returns an iterator pointing to the first element in the range [firstlast) that is greater than value, or last if no such element is found. The range [firstlast) 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 niebloids, that is:

In practice, they may be implemented as function objects, or with special compiler extensions.

Contents

[edit] 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

[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 log
2
(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<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;

[edit] 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

[edit] See also

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