## mismatch

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:

• InputIterator1 is a model of Input Iterator.

• InputIterator2 is a model of Input Iterator.

• InputIterator1's value type is a model of Equality Comparable.

• InputIterator2's value type is a model of Equality Comparable.

• InputIterator1's value type can be compared for equality with InputIterator2's value type.

For the second version:

• InputIterator1 is a model of Input Iterator.

• InputIterator2 is a model of Input Iterator.

• BinaryPredicate is a model of Binary Predicate.

• 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;```