std::is_permutation in C++ STL

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 <iostream>#include <algorithm>  //Driver Codeint 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 <iostream>#include <algorithm>  /*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:
// Falseis_permutation ( c1.begin(),     c1.end (), c2.begin(), c2.end ())   // Trueis_permutation ( c1.begin() + 1, c1.end (), c2.begin(), c2.end ())  // True, all empty ranges are permutations of each otheris_permutation ( c1.end (), c1.end (), c2.end(), c2.end ())
Reference : Official C++ Documentation for std :: is_permutation
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