Illustrates how to use the prev_permutation Standard Template Library (STL) function in Visual C++.
template<class BidirectionalIterator> inline
bool prev_permutation(
BidirectionalIterator First,
BidirectionalIterator Last
)
Remarks
备注
The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.
The prev_permutation algorithm changes the order of the elements the range [First, Last), to the previous lexicographic permutation and returns true. If there is no prev_permutation, it arranges the sequence to be the first permutation and returns false.
备注
The prev_permutation algorithm assumes the sequence is sorted in descending order using operator<. The nonpredicate version uses the operator< to order the permutations.
Example
// prev_permutation.cpp
// compile with: /EHsc
// Illustrates how to use the prev_permutation
// function.
//
// Functions:
// prev_permutation : Change the order of the sequence to the
// previous lexicographic permutation.
// 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 ;
int 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, " ");
// location of first element of Pattern
start = Pattern.begin();
// one past the location last element of Pattern
end = Pattern.end();
//Initialize vector Pattern
Pattern[0] = "C";
Pattern[1] = "B";
Pattern[2] = "A";
// print content of Pattern
cout << "Before calling prev_permutation..." << endl << "Pattern: [";
for (it = start; it != end; it++)
cout << " " << *it;
cout << " ]" << endl;
// Generate all possible permutations
cout << "After calling prev_permutation...." << endl;
while ( prev_permutation(start, end) )
{
cout << "[ ";
copy(start, end, outIt);
cout << "]" << endl;
}
}
Output
Before calling prev_permutation... Pattern: [ C B A ] After calling prev_permutation.... [ C A B ] [ B C A ] [ B A C ] [ A C B ] [ A B C ]
Requirements
Header: <algorithm>