std::lower_bound

 

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

Returns an iterator pointing to the first element in the range [first, last) that is not less than value. The first version uses operator< to compare the elements, the second version uses the given comparison function comp.

Parámetros

first, last	-	iterators defining the range to examine
value	-	valor para comparar los elementos a Original: value to compare the elements to The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 ForwardIt can be dereferenced and then implicitly converted to  Type1. The type  Type2 must be such that an object of type T can be implicitly converted to  Type2. ​
Type requirements
- ForwardIt must meet the requirements of ForwardIterator.

Valor de retorno

Iterator pointing to the first element that is not less than value, or last if no such element is found.

Complejidad

Logarítmica en la distancia entre first y last

Original:

Logarithmic in the distance between first and last

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You can help to correct and verify the translation. Click here for instructions.

Posible implementación

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

Ejemplo

#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

Ver también

equal_range	El rendimiento es de los elementos que coinciden con una clave específica Original: returns range of elements matching a specific key The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (función de plantilla)
upper_bound	devuelve un iterador al primer elemento' mayor que un cierto valor Original: returns an iterator to the first element greater than a certain value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (función de plantilla)