C++ Programming Code Examples
C++ > Visual C++ 5.0 Standard C++ Library Code Examples
The next permutation algorithm changes the order of the elements in the range
The next permutation algorithm changes the order of the elements in the range
The next permutation algorithm changes the order of the elements in the range
next_permutation
Header
<algorithm>
template<class BidirectionalIterator> inline
bool next_permutation(BidirectionalIterator first, BidirectionalIterator last)
The next_permutation algorithm changes the order of the elements in the range [first, last) to the next lexicographic permutation and returns true. If there is no next_permutation, it arranges the sequence to be the first permutation and returns false. IMPORTANT: The next_permutation algorithm assumes the sequence is sorted in ascending order using operator<. The non-predicate version uses the operator< to order the permutations.
template<class BidirectionalIterator, class Compare> inline
bool next_permutation(BidirectionalIterator first, BidirectionalIterator last, Compare compare)
The next_permutation algorithm changes the order of the elements in the range [first, last) to the next lexicographic permutation and returns true. If there is no next_permutation, it arranges the sequence to be the first permutation and returns false. NOTE: The next_permutation algorithm assumes that the sequence is sorted in ascending order using the compare function. The non-predicate version uses the compare function to order the permutations.
Samples
Sample for Non-Predicate Version
// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <functional>
using namespace std ;
void main()
{
const int VECTOR_SIZE = 3 ;
// Define a template class vector of strings
typedef vector<string> StrVector ;
//Define an iterator for template class vector of strings
typedef StrVector::iterator StrVectorIt ;
//Define an ostream iterator for strings
typedef ostream_iterator<string> StrOstreamIt;
StrVector Pattern(VECTOR_SIZE) ;
StrVectorIt start, end, it ;
StrOstreamIt outIt(cout, " ") ;
start = Pattern.begin() ; // location of first
// element of Pattern
end = Pattern.end() ; // one past the location last
// element of Pattern
//Initialize vector Pattern
Pattern[0] = "A" ;
Pattern[1] = "B" ;
Pattern[2] = "C" ;
// print content of Pattern
cout << "Before calling next_permutation...\n" << "Pattern: " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << "\n\n" ;
// Generate all possible permutations
cout << "After calling next_permutation...." << endl ;
while ( next_permutation(start, end) )
{
copy(start, end, outIt) ;
cout << endl ;
}
}
Program Output
Before calling next_permutation:
Pattern: A B C
After calling next_permutation:
A C B
B A C
B C A
C A B
C B A
Sample for Predicate Version
// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <functional>
using namespace std ;
void main()
{
const int VECTOR_SIZE = 3 ;
// Define a template class vector of strings
typedef vector<string> StrVector ;
//Define an iterator for template class vector of strings
typedef StrVector::iterator StrVectorIt ;
//Define an ostream iterator for strings
typedef ostream_iterator<string> StrOstreamIt;
StrVector Pattern(VECTOR_SIZE) ;
StrVectorIt start, end, it ;
StrOstreamIt outIt(cout, " ") ;
start = Pattern.begin() ; // location of first
// element of Pattern
end = Pattern.end() ; // one past the location last
// element of Pattern
//Initialize vector Pattern
Pattern[0] = "K" ;
Pattern[1] = "A" ;
Pattern[2] = "L" ;
//sort the contents of Pattern, required by next_permutation
sort(start, end, less<string>()) ;
// print content of Pattern
cout << "Before calling next_permutation...\n" << "Pattern: " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << "\n\n" ;
// Generate all possible permutations
cout << "After calling next_permutation...." << endl ;
while ( next_permutation(start, end, less<string>()) )
{
copy(start, end, outIt) ;
cout << endl ;
}
}
Program Output
Before calling next_permutation:
Pattern: A K L
After calling next_permutation:.
A L K
K A L
K L A
L A K
L K A
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Transform range to next permutation. Rearranges the elements in the range [first,last) into the next lexicographically greater permutation. A permutation is each one of the N! possible arrangements the elements can take (where N is the number of elements in the range). Different permutations can be ordered according to how they compare lexicographicaly to each other; The first such-sorted possible permutation (the one that would compare lexicographically smaller to all other permutations) is the one which has all its elements sorted in ascending order, and the largest has all its elements sorted in descending order. The comparisons of individual elements are performed using either operator< for the first version, or comp for the second.
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Function object class for less-than inequality comparison. Binary function object class whose call returns whether the its first argument compares less than the second (as returned by operator <). Generically, function objects are instances of a class with member function operator() defined. This member function allows the object to be used with the same syntax as a function call. This function does not return any value.
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