std::mismatch
Defined in header <algorithm>
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template< class InputIt1, class InputIt2 > std::pair<InputIt1, InputIt2> |
(1) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > std::pair<ForwardIt1, ForwardIt2> |
(2) | (since C++17) |
template< class InputIt1, class InputIt2, class BinaryPred > std::pair<InputIt1, InputIt2> |
(3) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class BinaryPred > |
(4) | (since C++17) |
template< class InputIt1, class InputIt2 > std::pair<InputIt1, InputIt2> |
(5) | (since C++14) (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > std::pair<ForwardIt1, ForwardIt2> |
(6) | (since C++17) |
template< class InputIt1, class InputIt2, class BinaryPred > std::pair<InputIt1, InputIt2> |
(7) | (since C++14) (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class BinaryPred > |
(8) | (since C++17) |
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.
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) |
Contents |
[edit] 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. |
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); 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) |
Type requirements | ||
-InputIt1 must meet the requirements of LegacyInputIterator.
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-InputIt2 must meet the requirements of LegacyInputIterator.
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-ForwardIt1 must meet the requirements of LegacyForwardIterator.
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-ForwardIt2 must meet the requirements of LegacyForwardIterator.
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-BinaryPred must meet the requirements of BinaryPredicate.
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[edit] 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::distance(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.
[edit] Complexity
Given N1 as std::distance(first1, last1) and N2 as std::distance(first2, last2):
[edit] Exceptions
The overloads with a template parameter named ExecutionPolicy
report errors 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 otherExecutionPolicy
, the behavior is implementation-defined. - If the algorithm fails to allocate memory, std::bad_alloc is thrown.
[edit] Possible implementation
mismatch (1) |
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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, BinaryPred 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); } |
[edit] 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).
#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.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
determines if two sets of elements are the same (function template) | |
(C++11) |
finds the first element satisfying specific criteria (function template) |
returns true if one range is lexicographically less than another (function template) | |
searches for the first occurrence of a range of elements (function template) | |
(C++20) |
finds the first position where two ranges differ (algorithm function object) |