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

[edit] 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.

[edit] 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.

[edit] Complexity

At most last1 - first1 applications of the predicate

[edit] Equivalent function

[edit] Example

This program determines the the longest substring that is simultaneously found at the very beginning of the given string and at the very end of it, in reverse order (possibly overlapping)

#include <iostream>
#include <string>
#include <algorithm>
 
std::string mirror_ends(const std::string& in)
{
    return std::string(in.begin(),
                       std::mismatch(in.begin(), in.end(), in.rbegin()).first);
}
 
int main()
{
    std::cout << mirror_ends("abXYZba") << '\n'
              << mirror_ends("abca") << '\n'
              << mirror_ends("aba") << '\n';
}

Output:

ab
a
aba

[edit] See also

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


(C++11)
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)