std::mismatch

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Defined in header <algorithm>

template< class InputIterator1, class InputIterator2 >

std::pair< InputIterator1, InputIterator2 >
    mismatch( InputIterator1 first1,
              InputIterator1 last1,

              InputIterator2 first2 );
(1)
template< class InputIterator1, class InputIterator2, class BinaryPredicate >

std::pair< InputIterator1, InputIterator2 >
    mismatch( InputIterator1 first1,
              InputIterator1 last1,
              InputIterator2 first2,

              BinaryPredicate p );
(2)

Returns the first mismatching pair of elements from two ranges: one defined by [first1, last1) and another starting at first2. The first version of the function uses operator== to compare the elements, the second version uses the given binary predicate p.

Contents

Parameters

first1, last1 - the first range of the elements
first2 - the beginning of the second range of the elements
p - binary predicate which returns ​true if the elements should be treated as equal.

The signature of the predicate function should be equivalent to the following:

bool pred(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 types ​Type1​ and ​Type2​ must be such that objects of types ​InputIterator1​ and ​InputIterator2​ can be dereferenced and then implicitly converted to ​Type1​ and ​Type2​ respectively.

Return value

std::pair with iterators to the first two non-equivalent elements, or, if no different elements found, pair with last1 and the corresponding iterator from the second range.

Complexity

linear in the distance between first1 and last1

Equivalent function

First version:
template<class InputIterator1, class InputIterator2>
std::pair<InputIterator1, InputIterator2>
    mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2)
{
    for (; first1 != last1; ++first1, ++first2) {
        if (*first1 != *first2) {
            return std::make_pair(first1, first2);
        }
    }
    return std::make_pair(first1, first2);
}
Second version:
template<class InputIterator1, class InputIterator2, class BinaryPredicate>
std::pair<InputIterator1, InputIterator2>
    mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, BinaryPredicate p)
{
    for (; first1 != last1; ++first1, ++first2) {
        if (!p(*first1, *first2)) {
            return std::make_pair(first1, first2);
        }
    }
    return std::make_pair(first1, first2);
}

Example

See also

equal
determines if two sets of elements are the same
(function template)
find
find_if
find_if_not


(C++0x)
finds the first element satisfying specific criteria
(function template)
lexicographical_compare
returns true if one range is lexicographically less than another
(function template)
search
searches for a range of elements
(function template)
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