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std::mismatch(3)	       C++ Standard Libary		std::mismatch(3)

NAME
     std::mismatch - std::mismatch

Synopsis
	Defined in header <algorithm>
	template< class InputIt1, class InputIt2 >

	std::pair<InputIt1,  InputIt2>				  (1) (constexpr
     since C++20)
	    mismatch( InputIt1 first1, InputIt1 last1,

		      InputIt2 first2 );
	template< class ExecutionPolicy, class ForwardIt1, class
	ForwardIt2 >

	std::pair<ForwardIt1,  ForwardIt2>			    (2)   (since
     C++17)
	    mismatch( ExecutionPolicy&& policy,
		      ForwardIt1 first1, ForwardIt1 last1,

		      ForwardIt2 first2 );
	template< class InputIt1, class InputIt2, class
	BinaryPred >

	std::pair<InputIt1,  InputIt2>				  (3) (constexpr
     since C++20)
	    mismatch( InputIt1 first1, InputIt1 last1,

		      InputIt2 first2, BinaryPred p );
	template< class ExecutionPolicy,

		  class ForwardIt1, class ForwardIt2, class
	BinaryPred >
	std::pair<ForwardIt1,  ForwardIt2>			    (4)   (since
     C++17)
	    mismatch( ExecutionPolicy&& policy,
		      ForwardIt1 first1, ForwardIt1 last1,

		      ForwardIt2 first2, BinaryPred p );
	template< class InputIt1, class InputIt2 >

	std::pair<InputIt1,   InputIt2> 			     (5)  (since
     C++14)
	    mismatch( InputIt1 first1, InputIt1 last1,		      (constexpr
     since C++20)

		      InputIt2 first2, InputIt2 last2 );
	template< class ExecutionPolicy, class ForwardIt1, class
	ForwardIt2 >

	std::pair<ForwardIt1,	ForwardIt2>			     (6)  (since
     C++17)
	    mismatch( ExecutionPolicy&& policy,
		      ForwardIt1 first1, ForwardIt1 last1,

		      ForwardIt2 first2, ForwardIt2 last2 );
	template< class InputIt1, class InputIt2, class
	BinaryPred >

	std::pair<InputIt1,  InputIt2>				    (7)   (since
     C++14)
	    mismatch(  InputIt1 first1, InputIt1 last1, 	      (constexpr
     since C++20)

		      InputIt2 first2, InputIt2 last2,
	BinaryPred p );
	template< class ExecutionPolicy,

		  class ForwardIt1, class ForwardIt2, class
	BinaryPred >
	std::pair<ForwardIt1,  ForwardIt2>			    (8)   (since
     C++17)
	    mismatch( ExecutionPolicy&& policy,
		      ForwardIt1 first1, ForwardIt1 last1,

		      ForwardIt2 first2, ForwardIt2 last2,
	BinaryPred p );

	Returns a pair of iterators to the first mismatching of elements from
	[first1, last1) and a range starting from first2:

	  *  For  overloads  (1-4),  the  second range has std::distance(first1,
     last1) elements.
	  * For overloads (5-8), the second range is [first2, last2).

	  * If std::distance(first1, last1) and std::distance(first2, last2) are
     different,
	    the comparison stops when last1 or last2 is reached.
	1,5) Elements are compared using operator==.
	3,7) Elements are compared using the given binary predicate p.
	2,4,6,8) Same as (1,3,5,7), but executed according to policy.
	These overloads participate in overload resolution only if

	std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>    is    true.
     (until
										  C++20)
	std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>      is
     true. (since
										  C++20)

Parameters
	first1, last1 - the first range of the elements
	first2, last2 - the second range of the elements
	policy	      - the execution policy to use. See  execution  policy  for
     details.
			binary	predicate  which  returns  true  if the elements
     should be
			treated as equal.

			The signature of the predicate function should be equiv-
     alent to the
			following:

			 bool pred(const Type1 &a, const Type2 &b);

	p	      - 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  regard-
     less 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  objects  of
     types
			InputIt1  and  InputIt2 can be dereferenced and then im-
     plicitly
			converted to Type1 and Type2 respectively.

Type requirements
	-
	InputIt1 must meet the requirements of LegacyInputIterator.
	-
	InputIt2 must meet the requirements of LegacyInputIterator.
	-
	ForwardIt1 must meet the requirements of LegacyForwardIterator.
	-
	ForwardIt2 must meet the requirements of LegacyForwardIterator.
	-
	BinaryPred must meet the requirements of BinaryPredicate.

Return value
	std::pair with iterators to the first two non-equal elements.

	If last1 is reached, the second iterator in the pair  is  the  std::dis-
     tance(first1,
	last1)
	th iterator after first2.

	For overloads (5-8), if last2 is reached, the first iterator in the pair
     is the
	std::distance(first2, last2)
	th iterator after first1.

Complexity
	Given \(\scriptsize N_1\)N
	1 as std::distance(first1, last1) and \(\scriptsize N_2\)N
	2 as std::distance(first2, last2):

	1,2) At most \(\scriptsize N_1\)N
	1 comparisons using operator==.
	3,4) At most \(\scriptsize N_1\)N
	1 applications of the predicate p.
	5,6) At most \(\scriptsize \min(N_1,N_2)\)min(N
	1,N
	2) comparisons using operator==.
	7,8) At most \(\scriptsize \min(N_1,N_2)\)min(N
	1,N
	2) applications of the predicate p.

Exceptions
	The overloads with a template parameter named ExecutionPolicy report er-
     rors as
	follows:

	  *  If  execution of a function invoked as part of the algorithm throws
     an exception
	    and ExecutionPolicy is one of the standard policies,  std::terminate
     is called.
	    For  any  other  ExecutionPolicy, the behavior is implementation-de-
     fined.
	  * If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation
					 mismatch (1)
	template<class InputIt1, class InputIt2>
	std::pair<InputIt1, InputIt2>
	    mismatch(InputIt1 first1, InputIt1 last1, InputIt2 first2)
	{
	    while (first1 != last1 && *first1 == *first2)
		++first1, ++first2;

	    return std::make_pair(first1, first2);
	}
					 mismatch (3)
	template<class InputIt1, class InputIt2, class BinaryPred>
	std::pair<InputIt1, InputIt2>
	    mismatch(InputIt1 first1, InputIt1	last1,	InputIt2  first2,  Bina-
     ryPred p)
	{
	    while (first1 != last1 && p(*first1, *first2))
		++first1, ++first2;

	    return std::make_pair(first1, first2);
	}
					 mismatch (5)
	template<class InputIt1, class InputIt2>
	std::pair<InputIt1, InputIt2>
	    mismatch(InputIt1  first1, InputIt1 last1, InputIt2 first2, InputIt2
     last2)
	{
	    while (first1 != last1 && first2 != last2 && *first1 == *first2)
		++first1, ++first2;

	    return std::make_pair(first1, first2);
	}
					 mismatch (7)
	template<class InputIt1, class InputIt2, class BinaryPred>
	std::pair<InputIt1, InputIt2>
	    mismatch(InputIt1 first1, InputIt1 last1,
		     InputIt2 first2, InputIt2 last2, BinaryPred p)
	{
	    while (first1 != last1 && first2 != last2 && p(*first1, *first2))
		++first1, ++first2;

	    return std::make_pair(first1, first2);
	}

Example
	This program determines 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).

     // Run this code

      #include <algorithm>
      #include <iostream>
      #include <string>

      std::string mirror_ends(const std::string& in)
      {
	  return std::string(in.begin(),
			     std::mismatch(in.begin(),	   in.end(),	 in.rbe-
     gin()).first);
      }

      int main()
      {
	  std::cout << mirror_ends("abXYZba") << '\n'
		    << mirror_ends("abca") << '\n'
		    << mirror_ends("aba") << '\n';
      }

Output:
      ab
      a
      aba

See also
	equal			determines if two sets of elements are the same
				(function template)
	find
	find_if 		finds the first element satisfying specific cri-
     teria
	find_if_not		(function template)
	(C++11)
				returns true if one range  is  lexicographically
     less than
	lexicographical_compare another
				(function template)
	search			searches for a range of elements
				(function template)
	ranges::mismatch	finds the first position where two ranges differ
	(C++20) 		(niebloid)

http://cppreference.com 	   2024.06.10			std::mismatch(3)
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