#include <stdio.h>

void swap ( int &a, int &b ) {
  int t = a;
  a = b;
  b = t;
}

void permsrec ( int n, int *temp, int level ) {
  if ( level == n ) {
    // terminate recutsion and print out
    for ( int i=0; i<n-1; i++ )
      printf ( "%i, ", temp[i] );
    printf ( "%i \n", temp[n-1] );
    return;
  }
  // level is a parting index in temp: on the left there are 
  // used numbers, on the right, free numbers
  for ( int i=level; i<n; i++ ) {
    // move number i from the right to the left, then recurse
    swap ( temp[level], temp[i] );
    permsrec ( n, temp, level+1 );
    // when done, undo the operation
    swap ( temp[level], temp[i] );  
  }
}

void perms ( int n ) {
  int *temp = new int[n];
  for ( int i=0; i<n; i++ ) temp[i] = i;
  permsrec ( n, temp, 0 );
  delete [] temp;
}


void main ( ) {
  perms ( 4 );
}