Defined in header <algorithm>  

(1)  
template< class BidirIt > bool next_permutation( BidirIt first, BidirIt last );  (until C++20)  
template< class BidirIt > constexpr bool next_permutation( BidirIt first, BidirIt last );  (since C++20)  
(2)  
template< class BidirIt, class Compare > bool next_permutation( BidirIt first, BidirIt last, Compare comp );  (until C++20)  
template< class BidirIt, class Compare > constexpr bool next_permutation( BidirIt first, BidirIt last, Compare comp );  (since C++20) 
Permutes the range [first, last)
into the next permutation, where the set of all permutations is ordered lexicographically with respect to operator<
or comp
. Returns true
if such a "next permutation" exists; otherwise transforms the range into the lexicographically first permutation (as if by std::sort(first, last, comp)
) and returns false
.
first, last    the range of elements to permute 
comp    comparison function object (i.e. an object that satisfies the requirements of Compare) which returns true if the first argument is less than the second. The signature of the comparison function should be equivalent to the following:
While the signature does not need to have 
Type requirements  
BidirIt must meet the requirements of ValueSwappable and LegacyBidirectionalIterator. 
true
if the new permutation is lexicographically greater than the old. false
if the last permutation was reached and the range was reset to the first permutation.
Any exceptions thrown from iterator operations or the element swap.
At most N/2 swaps, where N = std::distance(first, last)
. Averaged over the entire sequence of permutations, typical implementations use about 3 comparisons and 1.5 swaps per call.
Implementations (e.g. MSVC STL) may enable vectorization when the iterator type satisfies LegacyContiguousIterator and swapping its value type calls neither nontrivial special member function nor ADLfound swap
.
template<class BidirIt> bool next_permutation(BidirIt first, BidirIt last) { auto r_first = std::make_reverse_iterator(last); auto r_last = std::make_reverse_iterator(first); auto left = std::is_sorted_until(r_first, r_last); if(left != r_last){ auto right = std::upper_bound(r_first, left, *left); std::iter_swap(left, right); } std::reverse(left.base(), last); return left != r_last; } 
The following code prints all three permutations of the string "aba"
#include <algorithm> #include <string> #include <iostream> int main() { std::string s = "aba"; std::sort(s.begin(), s.end()); do { std::cout << s << '\n'; } while(std::next_permutation(s.begin(), s.end())); }
Output:
aab aba baa
(C++11)  determines if a sequence is a permutation of another sequence (function template) 
generates the next smaller lexicographic permutation of a range of elements (function template) 

(C++20)  generates the next greater lexicographic permutation of a range of elements (niebloid) 
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