void inshuffle(It it, std::size_t n) {
if (n==0) return;
for (std::size_t i = 0; 2*i < n; ++i) {
std::size_t k = 2*i + 1;
while (2*k <= n) k *= 2;
typename std::iterator_traits<It>::value_type tmp = it[n+i];
it[n+i] = it[k-1];
while (k % 2 == 0) {
it[k-1] = it[(k/2)-1];
k /= 2;
}
it[k-1] = tmp;
}
std::size_t kmin = 1;
while (2*kmin <= n) kmin *= 2;
for (std::size_t i = 0; 4*i+1 < n; ++i) {
std::size_t k = 2*i + 1;
while (2*k <= n) k *= 2;
std::size_t k1 = 2*(i+1) + 1;
while (2*k1 <= n) k1 *= 2;
if (k > k1) {
if (k1 < kmin) {
kmin = k1;
inshuffle(it+n, i+1);
}
else
inshuffle(it+n+1, i);
}
}
return inshuffle(it+n+(n%2), n/2);
}
void inshuffle(It it, std::size_t n) {
while (n > 0) {
std::size_t kmin = 1;
while (kmin <= n)
kmin *= 2;
{
std::size_t kk = kmin/2;
It itn = it + n;
for (std::size_t i = 0, s = (n+1)/2; i < s; ++i) {
std::size_t k = (2*i+1)*kk;
while (k > n) {
k /= 2;
kk /= 2;
}
// apply the cyclic permutation
typename std::iterator_traits<It>::value_type tmp = itn[i];
itn[i] = it[k-1];
while (k % 2 == 0) {
it[k-1] = it[(k/2)-1];
k /= 2;
}
it[k-1] = tmp;
}
}
// the optimized computation of k fails for n=2,
// so skip the 'normalization' loop when possible
if (n > 3) {
std::size_t kk = kmin/4;
for (std::size_t i = 1; 4*i < n+3; ++i) {
std::size_t k = (2*i+1)*kk;
if (k > n) {
kk /= 2;
if (k < kmin) {
kmin = k;
// if kmin is updated, do an in-shuffle
inshuffle(it+n, i);
}
else
// otherwise do an out-shuffle
inshuffle(it+n+1, i-1);
}
}
}
// implement the tail recursion as an iteration
it += n+(n%2);
n /= 2;
}
}
typename boost::enable_if< is_complex< typename bindings::value_type< VectorW >::type >, void >::type
interlace (VectorW& w) {
typedef typename bindings::value_type< VectorW >::type value_type;
typedef typename bindings::remove_imaginary< value_type >::type real_type;
value_type* pw = bindings::begin_value(w);
std::ptrdiff_t n = bindings::end_value(w) - pw;
if (n < 2) return;
inshuffle(reinterpret_cast<real_type*> (pw)+1, n-1);
}
int main(){
int n;
int i;
int *A;
printf("Enter the value of n, (total size of array = 2n): ");
scanf("%d",&n);
A = (int *)malloc((2*n+1)*sizeof(int));
for (i = 0; i <= 2*n; i++){
A[i] = i;
}
inshuffle(A,2*n);
printf("\n[");
for (i = 1; i <= 2*n; i ++){
printf(" %d",A[i]);
}
printf(" ]\n");
free(A);
return 1;
}
