Next_permutation (full permutation algorithm)

The STL provides two algorithms for calculating the permutations and combinations of relationships, namely Next_permutation and prev_permutation.

First explain the whole arrangement, as the name implies, that is, a group of numbers of the whole arrangement of the case.

Next_permutation is a list of all the permutations of a group of numbers, but the order of the list has a certain rules, the following is about Next_permutation listed the rules of precedence ...

Rules

1. First from the end of the beginning to look forward to two adjacent elements, so that the first element is *i, the second element is *ii, and satisfies *i<*ii.

2. After finding such a group of adjacent elements, then from the end of the forward test, to find the first element greater than *i, so that the *j, the i,j element Swap (swap).

3. Sort all the elements after the II (reverse) backwards.

For example, assuming that there is a sequence {0,1,2,3,4}, the above algorithm is applied to get the "next" permutation in one step. In the picture, only the two adjacent elements that conform to "one element is *i, the second element is *ii, and satisfy *i<*ii" are not shown in the search for proper J, swap, and reversal operations.

0 1 2 3 4-"0 1 2 4 3-" 0 1 3 2 4-"0 1 3 4 2-" 0 1 4 2 3-"0 1 4 3 2 ...

Just contact is not to say very clearly, to a simple application

Full arrangement of outputs (0 1 2 3 4)

#include <iostream>
#include <algorithm>
using namespace Std;
int main ()
{
int ans[5]={0,1,2,3,4};
Sort (ans,ans+5); /* This sort can be used, because {0, 1,2,3,4} is already ordered */
DO/* Note this step, if it is a while loop, you need to output */
{
for (int i=0;i<5;++i)
cout<<ans[i]<< "";
cout<<endl;
}while (Next_permutation (ans,ans+5));
return 0;
}

Say so much first, wait for later to make up Ba ba ....

Next_permutation (full permutation algorithm)