Пространства имён
Варианты
Действия

std::binary_search

Материал из cppreference.com
 
 
Алгоритмы
Функции
Немодифицирующие линейные операции
Модифицирующие линейные операции
Разделение
Сортировка (на отсортированных промежутках)
Бинарный поиск (на отсортированных промежутках)
binary_search
equal_range
Множества (на отсортированных промежутках)
Куча
Минимум/максимум
Числовые операции
Библиотека C
 
Заголовочный файл <algorithm>
template< class ForwardIt, class T >
bool binary_search( ForwardIt first, ForwardIt last, const T& value );
(1)
template< class ForwardIt, class T, class Compare >
bool binary_search( ForwardIt first, ForwardIt last, const T& value, Compare comp );
(2)
Проверяет, отсортированный диапазон [first, last) содержит элемент, равный value. Первый вариант используется operator< для сравнения элементов, вторая версия использует данную функцию сравнения comp.
Original:
Checks if the sorted range [first, last) contains an element equal to value. The first version uses operator< to compare the elements, the second version uses the given comparison function comp.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Содержание

[править] Параметры

first, last -
диапазон элементов для изучения
Original:
the range of elements to examine
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
value -
Значение для сравнения элементов
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 T can be implicitly converted to  Type1. The type  Type2 must be such that an object of type ForwardIt can be dereferenced and then implicitly converted to  Type2. ​

Type requirements
-
ForwardIt must meet the requirements of ForwardIterator.

[править] Возвращаемое значение

true, если элемент, равный value найдено, false иначе.
Original:
true if an element equal to value is found, false otherwise.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[править] Сложность

Логарифмическая в расстоянии между first и last
Original:
Logarithmic in the distance between first and last
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[править] Возможная реализация

First version
template<class ForwardIt, class T>
bool binary_search(ForwardIt first, ForwardIt last, const T& value)
{
    first = std::lower_bound(first, last, value);
    return (first != last && !(value < *first));
}
Second version
template<class ForwardIt, class T, class Compare>
bool binary_search(ForwardIt first, ForwardIt last, const T& value, Compare comp)
{
    first = std::lower_bound(first, last, value);
    return (first != last && !(comp(value, *first));
}

[править] Пример

#include <iostream>
#include <algorithm>
#include <vector>
 
int main()
{
    std::vector<int> haystack {1, 3, 4, 5, 9};
    std::vector<int> needles {1, 2, 3};
 
    for (auto needle : needles) {
        std::cout << "Searching for " << needle << '\n';
        if (std::binary_search(haystack.begin(), haystack.end(), needle)) {
            std::cout << "Found " << needle << '\n';
        } else {
            std::cout << "no dice!\n";
        }
    }
}

Вывод:

Searching for 1
Found 1
Searching for 2
no dice!
Searching for 3
Found 3

[править] См. также

возвращает набор элементов для конкретного ключа
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.

(шаблон функции) [edit]