Nested do-while ?

**smokeyangel** · 04-28-2012

I don't really understand...

Originally Posted by bluefare

now the question is how can i make the output like this ;

1 2 3 4
1 2 4 3
2 1 3 4
2 1 4 3

if you realize first 2 number had made a permutation each other and the other last 2 number had a permutation each other ,

the example is about 4 number making and per 2 of them making permutation ( 2!*2!= 4 possible results )

So you are treating the group of 4 numbers as 2 separate groups of 2 and permuting them in turn? If that's what you mean then I don't agree with your number of results - I think it's 2!+2!=4 not 2!*2!=4. So for 9 numbers, 3 groups, we'd permute each set of 3 3! times, over 3 groups, means 3!+3!+3!=18 possible results not 108?

Like so:

Code:

Have I misunderstood?

from here if you give me the idea i will try to make this code for ' n '
like we say there are 9 number and per 3 of them makes permutation,(3! *3!*3! = 108 possible results)

So you have 2 variables -- N - number of numbers, and g, number of groups to split them into? Or do you infer the number of groups from N somehow?

If I've got any of that right, then you need 2 loops -- an outer loop that terminates when there aren't any more permutations, and an inner loop which cycles through the groups. I'd use a for loop for the inner loop (convenient to use the index for calculating the offsets to the various groups), and a while loop for the outer loop. Set a flag in the inner loop if no permutations happened, and use that to control the outer loop.

**bluefare** · 04-28-2012

Code:

#include <iostream>
#include <algorithm>
using namespace std;

int main ()
{
    int n=9;
    int myints[] = {1,2,3,4,5,6,7,8,9};
    do
    {
        do
        {
            do
            {
                for(int i=0 ; i<n ; i++)
                    cout << myints[i];
                cout<<endl;
            }
            while ( next_permutation (myints+6,myints+9) );
        }
        while ( next_permutation (myints+3,myints+6) );
    }
    while ( next_permutation (myints,myints+3) );
    return 0;
}

i have done so far but from now on i can not figure how to make recursive do-while loop because the array size can be inceased to 'n' in the example n=9 but later can be maybe 18 or something thanks

it is for 9 => 3!*3!*3! = 108 possible results

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