##### Personal tools

# next_permutation

**Click on the banner to return to the class reference home page.**

## next_permutation

Algorithm

- Summary
- Data Type and Member Function Indexes
- Synopsis
- Description
- Complexity
- Example
- Warning
- See Also

### Summary

Generate successive permutations of a sequence based on an ordering function.

### Data Type and Member Function Indexes

(exclusive of constructors and destructors)

None

### Synopsis

#include <algorithm> template <class BidirectionalIterator> boolnext_permutation(BidirectionalIterator first, BidirectionalIterator last); template <class BidirectionalIterator, class Compare> boolnext_permutation(BidirectionalIterator first, BidirectionalIterator last, Compare comp);

### Description

The permutation-generating algorithms (** next_permutation** and

**) assume that the set of all permutations 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.**

*prev_permutation*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,

**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.)**

*next_permutation*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.

### Complexity

At most (last - first)/2 swaps are performed.

### Example

// // 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,char>(cout," ")); cout << endl << " "; cout << "Previous permutation: "; copy(prev_m1.begin(),prev_m1.end(), ostream_iterator<int,char>(cout," ")); cout << endl<< " "; cout << "Next Permutation: "; copy(next_m1.begin(),next_m1.end(), ostream_iterator<int,char>(cout," ")); cout << endl << endl; cout << "Example 2: " << endl << " "; cout << "Original values: "; copy(m2.begin(),m2.end(), ostream_iterator<char,char>(cout," ")); cout << endl << " "; cout << "Previous Permutation: "; copy(prev_m2.begin(),prev_m2.end(), ostream_iterator<char,char>(cout," ")); cout << endl << " "; cout << "Next Permutation: "; copy(next_m2.begin(),next_m2.end(), ostream_iterator<char,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

### Warning

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<int> >

instead of :

vector<int>

### See Also

©Copyright 1996, Rogue Wave Software, Inc.