To create an arrangement of a re-set (method)

Through the method of violence or Dfs can easily get n number of the full array, can generate a re-set, such as an array a[], require the output of the array of the entire arrangement, and the normal perfection arrangement, the array is likely to have duplicate number, so the method needs to be changed:

Dfs

#include "iostream"
#include "CString"
#include "Cstdio"
using namespace Std;
int n,book[21],a[21];
int ca=1;

void Dfs (int step)
{
if ((step = = N))
{
for (int i=1;i<n;i++) cout<<a[i]<< ";
cout<<a[n]<<endl;
Return
}
for (int i=1;i<=n;i++)
if (book[i]<=2)//here means that the number of repetitions can have up to two
{
A[step+1]=i;
book[i]++;
DFS (STEP+1);
book[i]--;
}
}
int main ()
{
int x=1;
while (scanf ("%d", &n)!=eof)
{
A[1]=1;
if (x>1) cout<<endl;x++;
cout<< "Case" <<ca++<< ': ' <<endl;
DFS (0);
}
return 0;
}

Violence:

#include "iostream"
#include "CString"
#include "Cstdio"
using namespace Std;
int n,book[21],a[21];
int ca=1;

void print (int step)
{
if ((step = = n+1))
{
for (int i=1;i<n;i++) cout<<a[i]<< ";
cout<<a[n]<<endl;
}

for (int i=1;i<=n;i++)
{
int ok=1;
for (int j=2;j<step;j++)//Here j=2 means up to 2 duplicate numbers
if (a[j]==i) ok=0;
if (OK)
{
A[step]=i;
Print (step+1);
}
}
}

int main ()
{
int x=1;
while (scanf ("%d", &n)!=eof)
{
memset (A,0,sizeof (a));
if (x>1) cout<<endl;x++;
cout<< "Case" <<ca++<< ': ' <<endl;
Print (1);
}
return 0;
}

Finally, there is a STL function, more concise and useful

#include "iostream"
#include "algorithm"
using namespace Std;

int main ()
{
int n,p[10];
while (Cin>>n)
{
for (int i=0;i<n;i++) cin>>p[i];
Sort (p,p+n);
Do
{
for (int i=0;i<n;i++) cout<<p[i]<< ";
cout<<endl;
}while (Next_permutation (p,p+n));
}
return 0;
}

To create an arrangement of a re-set (method)