Algorithm
Generate successive permutations of a sequence based on an ordering function.
#include <algorithm>
template <class BidirectionalIterator> bool next_permutation (BidirectionalIterator first, BidirectionalIterator last); template <class BidirectionalIterator, class Compare> bool next_permutation (BidirectionalIterator first, BidirectionalIterator last, Compare comp);
The permutation-generating algorithms (next_permutation and prev_permutation) assume that the set of all permutions of the elements in a sequence is lexicographically sorted with respect to operator< or comp. So, for example, if a sequence includes the integers 1 2 3, that sequence has six permutations, which, in order from first to last are: 1 2 3 , 1 3 2, 2 1 3, 2 3 1, 3 1 2, and 3 2 1.
The next_permutation algorithm takes a sequence defined by the range [first, last) and transforms it into its next permutation, if possible. If such a permutation does exist, the algorithm completes the transformation and returns true. If the permutation does not exist, next_permutation returns false, and transforms the permutation into its "first" permutation (according to the lexicographical ordering defined by either operator<, the default used in the first version of the algorithm,or comp, which is user-supplied in the second version of the algorithm.)
For example, if the sequence defined by [first, last) contains the integers 3 2 1 (in that order), there is not a "next permutation." Therefore, the algorithm transforms the sequence into its first permutation (1 2 3) and returns false.
At most (last - first)/2 swaps are performed.
// // permute.cpp // #include <numeric> //for accumulate #include <vector> //for vector #include <functional> //for less #include <iostream.h> int main() { //Initialize a vector using an array of ints int a1[] = {0,0,0,0,1,0,0,0,0,0}; char a2[] = "abcdefghji";
//Create the initial set and copies for permuting vector<int> m1(a1, a1+10); vector<int> prev_m1((size_t)10), next_m1((size_t)10); vector<char> m2(a2, a2+10); vector<char> prev_m2((size_t)10), next_m2((size_t)10);
copy(m1.begin(), m1.end(), prev_m1.begin()); copy(m1.begin(), m1.end(), next_m1.begin()); copy(m2.begin(), m2.end(), prev_m2.begin()); copy(m2.begin(), m2.end(), next_m2.begin());
//Create permutations prev_permutation(prev_m1.begin(), prev_m1.end(),less<int>()); next_permutation(next_m1.begin(), next_m1.end(),less<int>()); prev_permutation(prev_m2.begin(), prev_m2.end(),less<int>()); next_permutation(next_m2.begin(), next_m2.end(),less<int>());
//Output results cout << "Example 1: " << endl << " "; cout << "Original values: "; copy(m1.begin(),m1.end(), ostream_iterator<int>(cout," ")); cout << endl << " "; cout << "Previous permutation: "; copy(prev_m1.begin(),prev_m1.end(), ostream_iterator<int>(cout," "));
cout << endl<< " "; cout << "Next Permutation: "; copy(next_m1.begin(),next_m1.end(), ostream_iterator<int>(cout," ")); cout << endl << endl;
cout << "Example 2: " << endl << " "; cout << "Original values: "; copy(m2.begin(),m2.end(), ostream_iterator<char>(cout," ")); cout << endl << " "; cout << "Previous Permutation: "; copy(prev_m2.begin(),prev_m2.end(), ostream_iterator<char>(cout," ")); cout << endl << " ";
cout << "Next Permutation: "; copy(next_m2.begin(),next_m2.end(), ostream_iterator<char>(cout," ")); cout << endl << endl; return 0; } Output : Example 1: Original values: 0 0 0 0 1 0 0 0 0 0 Previous permutation: 0 0 0 0 0 1 0 0 0 0 Next Permutation: 0 0 0 1 0 0 0 0 0 0 Example 2: Original values: a b c d e f g h j i Previous Permutation: a b c d e f g h i j Next Permutation: a b c d e f g i h j
If your compiler does not support default template parameters, the you need to always supply the Allocator template argument. For instance, you will need to write :
vector<int, allocator>
instead of :
vector<int>