# mismatch

 Category: algorithms Component type: function

## Prototype

Mismatch is an overloaded name; there are actually two mismatch functions.

template <class InputIterator1, class InputIterator2>
pair<InputIterator1, InputIterator2>
mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2);

template <class InputIterator1, class InputIterator2,
class BinaryPredicate>
pair<InputIterator1, InputIterator2>
mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2,
BinaryPredicate binary_pred);

## Description

Mismatch finds the first position where the two ranges [first1, last1) and [first2, first2 + (last1 - first1)) differ. The two versions of mismatch use different tests for whether elements differ.

The first version of mismatch finds the first iterator i in [first1, last1) such that *i != *(first2 + (i - first1)). The return value is a pair whose first element is i and whose second element is *(first2 + (i - first1)). If no such iterator i exists, the return value is a pair whose first element is last1 and whose second element is *(first2 + (last1 - first1)).

The second version of mismatch finds the first iterator i in [first1, last1) such that binary_pred(*i, (first2 + (i - first1)) is false. The return value is a pair whose first element is i and whose second element is *(first2 + (i - first1)). If no such iterator i exists, the return value is a pair whose first element is last1 and whose second element is *(first2 + (last1 - first1)).

## Definition

Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

## Requirements on types

For the first version:

For the second version:

• InputIterator1 is a model of InputIterator.
• InputIterator2 is a model of InputIterator.
• BinaryPredicate is a model of BinaryPredicate.
• InputIterator1's value type is convertible to BinaryPredicate's first argument type.
• InputIterator2's value type is convertible to BinaryPredicate's second argument type.

## Preconditions

• [first1, last1) is a valid range.
• [first2, first2 + (last2 - last1)) is a valid range.

## Complexity

Linear. At most last1 - first1 comparisons.

## Example

int A1[] = { 3, 1, 4, 1, 5, 9, 3 };
int A2[] = { 3, 1, 4, 2, 8, 5, 7 };
const int N = sizeof(A1) / sizeof(int);

pair<int*, int*> result = mismatch(A1, A1 + N, A2);
cout << "The first mismatch is in position " << result.first - A1 << endl;
cout << "Values are: " << *(result.first) << ", " << *(result.second) << endl;