std::upper_bound

 

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all_of any_of none_of (C++11) (C++11) (C++11) for_each count count_if mismatch equal	find find_if find_if_not (C++11) find_end find_first_of adjacent_find search search_n
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copy copy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n remove remove_if remove_copy remove_copy_if	replace replace_if replace_copy replace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffle shuffle   (C++11) unique unique_copy
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is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
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lower_bound upper_bound	binary_search equal_range
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C library
qsort	bsearch

 

Defined in header <algorithm>
template< class ForwardIterator, class T > ForwardIterator upper_bound( ForwardIterator first, ForwardIterator last,                              const T& value );	(1)
template< class ForwardIterator, class T, class Compare > ForwardIterator upper_bound( ForwardIterator first, ForwardIterator last,                              const T& value, Compare comp );	(2)

Returns an iterator pointing to the first element in the range [first, last) that is greater than value. The first version uses operator< to compare the elements, the second version uses the given comparison function comp.

Parameters

first, last	-	the range of elements to examine
value	-	value to compare the elements to
comp	-	comparison function which returns ​true if the first argument is less than the second. The signature of the comparison function should be equivalent to the following: bool cmp(const Type1 &a, const Type2 &b); The signature does not need to have const &, but the function must not modify the objects passed to it. The type  Type1 must be such that an object of type T can be implicitly converted to  Type1. The type  Type2 must be such that an object of type ForwardIterator can be dereferenced and then implicitly converted to  Type2. ​

Return value

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

Possible implementation

First version
template<class ForwardIterator, class T> ForwardIterator upper_bound(ForwardIterator first, ForwardIterator last, const T& value) { ForwardIterator it; std::iterator_traits<ForwardIterator>::distance_type count, step; count = std::distance(first,last);   while (count > 0) { it = first; step = count / 2; std::advance(it, step); if (!(value < *it)) { first = ++it; count -= step + 1; } else count = step; } return first; }
Second version
template<class ForwardIterator, class T, class Compare> ForwardIterator upper_bound(ForwardIterator first, ForwardIterator last, const T& value, Compare comp) { ForwardIterator it; std::iterator_traits<ForwardIterator>::distance_type count, step; count = std::distance(first,last);   while (count > 0) { it = first; step = count / 2; std::advance(it, step); if (!comp(value, *it)), first = ++it; count -= step + 1 } else count = step; } return first; }

Example

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
 
int main()
{
    std::vector<int> data = { 1, 1, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 6 };
 
    auto lower = std::lower_bound(data.begin(), data.end(), 4);
    auto upper = std::upper_bound(data.begin(), data.end(), 4);
 
    std::copy(lower, upper, std::ostream_iterator<int>(std::cout, " "));
}

Output:

4 4 4

Complexity

logarithmic in the distance between first and last

See also

equal_range	returns range of elements matching a specific key (function template)
lower_bound	returns an iterator to the first element not less than the given value (function template)