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std::is_permutation in C++ STL
• Difficulty Level : Medium
• Last Updated : 06 Jul, 2017

The C++ function std::algorithm::is_permutation() tests whether a sequence is permutation of other or not. It uses operator == for comparison. This function was defined in C++11.
Syntax:

```template <class ForwardIterator1, class ForwardIterator2 >
bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2);

first1, last1: Input iterators to the initial
and final positions of the first sequence.
first2 : Input iterator to the initial position of the second sequence.

Return value :
true : if all the elements in range [first1, last1]
compare equal to those of the range
starting at first2 in any order.
false : Any element missing or exceeding.```

The function considers as many elements of this sequence as those in the range [first1, last1]. If this sequence is shorter, it causes undefined behaviour.

 `// CPP program to check if ``// two arrays are equal or not``// using std :: is_permutation``#include ``#include `` ` `//Driver Code``int` `main()``{``    ``int` `A[] = {1, 7, 0, 2};``    ``int` `B[] = {0, 7, 2, 1};``     ` `    ``// Check if array B includes all elements of ``    ``// array A``    ``if` `( std :: is_permutation ( A, A+4, B ) )``    ``{``        ``std :: cout << ``"B is a permutation of A"` `;``    ``}``     ` `    ``else``    ``{``        ``std :: cout << ``"B is not a permutation of A"` `;``    ``}``    ``return` `0;``}`

Output:

```B is a permutation of A
```

Other approach to find if arrays are equal or not is discussed here .

Another Example: Check whether two strings are anagram of each other

 `// CPP program to check whether two strings ``// are anagram of each other``// using std :: is_permutation``#include ``#include `` ` `/*Driver Code*/``int` `main()``{``    ``std :: string A = ``"SILENT"``;``    ``std :: string B = ``"LISTEN"``;``     ` `    ``/*Checking if B is a permutation of A*/``    ``if` `( is_permutation ( A.begin(), A.end(), B.begin() ) )``    ``{``        ``std :: cout << ``"Anagrams"` `;``    ``}``     ` `    ``else``    ``{``        ``std :: cout << ``"Not Anagrams"` `;``    ``}``    ``return` `0;``}`

Output:

```Anagrams
```

Other approach to Check whether two strings are anagram of each other is discussed here .

Versions of std::permutation

```template< class ForwardIt1, class ForwardIt2 >
bool is_permutation( ForwardIt1 first1, ForwardIt1 last1,
ForwardIt2 first2 );
// (since C++11)
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate >
bool is_permutation( ForwardIt1 first1, ForwardIt1 last1,
ForwardIt2 first2, BinaryPredicate p );
// (since C++11)
template< class ForwardIt1, class ForwardIt2 >
bool is_permutation( ForwardIt1 first1, ForwardIt1 last1,
ForwardIt2 first2, ForwardIt2 last2 );
// (since C++14)
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate >
bool is_permutation( ForwardIt1 first1, ForwardIt1 last1,
ForwardIt2 first2, ForwardIt2 last)2,
BinaryPredicate p );
//(since C++14)

first1, last1 : the range of elements to compare
first2, last2 : the second range to compare
p : binary predicate which returns ​true if the elements should be treated as equal.
```

Examples:

 `// False``is_permutation ( c1.begin(),     c1.end (), c2.begin(), c2.end ()) `` ` `// True``is_permutation ( c1.begin() + 1, c1.end (), c2.begin(), c2.end ())`` ` `// True, all empty ranges are permutations of each other``is_permutation ( c1.end (), c1.end (), c2.end(), c2.end ())`

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