std::binary_search

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Defined in header <algorithm>

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template< class ForwardIterator, class T >

bool binary_search( ForwardIterator first, ForwardIterator last,

const T& value );

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template< class ForwardIterator, class T, class Compare >

bool binary_search( ForwardIterator first, ForwardIterator last,

const T& value, Compare comp );

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Checks if the sorted range [first, last) contains an element equal to value. The first version uses Template:cpp to compare the elements, the second version uses the given comparison function comp.

Template:params

first, last - the range of elements to examine

value - value to compare the elements to

comp

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comparison function object (i.e. an object that satisfies the requirements of Compare) 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);

While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy(since C++11)).
The types Type1 and Type2 must be such that an object of type T can be implicitly converted to both Type1 and Type2, and an object of type ForwardIterator can be dereferenced and then implicitly converted to both Type1 and Type2.